Two views of N3297 photographed in October 1941, during testing at Boscombe Down. Note the 'bumps' at the rear of the makeshift cowling. The aircraft was a hybrid, combining the modified Mk.III fuselage (similar to the later Mk.VIII), 'A' wing (without armament), and Merlin 61. In the original Mk.III prototype, to make room for enlarged fuel tanks in the fuselage, the upper portion of the fireproof bulkhead was inclined forward, as was the corresponding panel line between the main tank cover and the engine cowling. This was retained in N3297 throughout her life. Similar slant upper bulkhead/cowling arrangement would be used in just a few initial Mk.V-to-IX conversions, but would later be adopted as standard in Griffon-engined Spitfires. The upper surface painting scheme seems to have been Temperate Land in which N3297 was first finished in 1940 (not being a Fighter Command machine, the Spitfire was not affected by the switch to grey-and-green Day Fighter scheme in mid-1941). Undersides were yellow, as prescribed for prototypes (ortochromatic photos rendered this colour rather dark, as clearly displayed by the outer ring of the fuselage roundel). The propeller spinner looks like Sky, not usual on prototypes.

AA873 was the first Mk.V with 'C' wing, and later became one of the earliest Mk.Vs converted to Mk.IX at Hucknall. These photos show the Spitfire in the original form, during 'C' wing trials at Boscombe Down in early 1942. Note the heaviest weapon combination of four 20mm cannon. Typical features of those Supermarine-built Mk.VCs allocated for conversion to Mk.IX standard by Rolls-Royce included the short-spinner de Havilland propeller and the later style windscreen with integral bullet-proof panel. The upper engine cowling features the standard assortment of tiny tear-drop shaped fairings near the rearmost exhaust stack. Note also the standard positions in which the serial and the fuselage roundel were applied by Supermarine. Curiously, this Spitfire (as shown) was fitted with the wire aerial between the mast and the rudder, normally used with the HF radio. From the end of the Battle of Britain on, Fighter Command aircraft used VHF radio sets that required no such wire aerial. Following conversion to Mk.IX standard, AA873 was allocated to 64 Squadron for operational trials in June 1942, after which the Spitfire was returned to Rolls-Royce in July, and spent the rest of her life as a test machine

A well-known shot of 152 Squadron Spitfire IXs and Vs at an Italian airfield in 1943. Note the distinctively dark appearance of the bottom colour on these aircraft. MA454 'UM-V' in the foreground had the early type tailplane/elevator, but the later, single-blister cannon covers. 'UM-Q', further down the line, was one of the first CBAF-built Mk.IXs (JL100 range), and featured the large double-blister covers. It is noteworthy that the camouflage colours on 'UM-Z' (at far left, serial also in MAxxx range) appear transposed.

Five to Nine Noses and Tails. 1. Original Mk.V cowling of the aircraft earmarked for conversion. 2. Early Rolls-Royce conversion with stretched Mk.V cowling. 3. Initial Supermarine production. (Later Supermarine production cowling, also used on late Rolls-Royce conversions, was virtually identical, except for the small teardrop fairing above the rearmost exhaust stack.) 4. CBAF production standard. 5. Production LF.IX. (The Aero-Vee filter bottom cowling was later retrofitted to many surviving F.IX aircraft during overhauls.) 6. Early style. (Fitted to all Supermarine-built or Rolls-Royce converted Spitfire F.IXs, and to CBAF-built F.IXs until MA600 range.) 7. Late style. (Fitted to CBAF-built F.IXs from MA600 range on, retrofitted to many earlier aircraft during overhauls.) 8 and 9. Rolls-Royce conversions - two extreme variations. 10. Typical Supermarine production. 11. Typical CBAF production.

BR143 'SZ-S' of 316 (Polish) Squadron, RAF Northolt, early 1943. One of the earliest converted by Rolls-Royce from Mk.VCs, this was delivered to 306 (Polish) Squadron in November 1942. It served with that unit until March 1943 when it was taken over by 316 Squadron. Available photographs show this in what appears to be the standard Day Fighter scheme on the upper surfaces with Medium Sea Grey unders. The 'he'he'he' on the rear fuselage seems to have been a personal inscription, partly obscured when the code letter was repainted. During repair after an accident in 1943, BR143 was fitted with some modified items (including a new style rear-view mirror), and recoded 'SZ-Q'.

EN526 'SZ-G', Northolt Wing, Northolt, mid-1943. A later Rolls-Royce conversion, this featured standard Supermarine-style engine cowlings, but the camouflage pattern on the nose was typical for a Hucknall-converted Mk.V. Technically allocated to 316 (Polish) Squadron, it was the personal mount of Wg Cdr Aleksander Gabszewicz, OC Northolt Wing during summer 1943. Several photographs of this aeroplane exist, taken on different occasions and under varying lighting conditions, and they all prove that EN526 was not finished in a standard scheme. The upper colour occupying the position of Ocean Grey was very light, in some photos it appears lighter than the bottom colour (which should be Medium Sea Grey). It is difficult to ascertain the actual shades, so this profile should be regarded as speculative.

BS342 'R', 238 Squadron, El Gamil (Port Said), Egypt, 1943. One of the last Rolls-Royce conversions still featuring the makeshift stretched Mk.VC cowlings, this Spitfire was delivered to the Mediterranean. No.238 Squadron provided air defence of the Suez Canal at that time, and BS342 must have been earmarked for high-altitude interceptions, judging by the pointed wingtips and the painting scheme. Note that the Spitfire had had its radio aerial (ie probably the entire radio set) and the outer cannon stubs removed - probably in order to reduce weight and thus improve high-altitude performance. Another noteworthy feature was the 'Aboukir' style dust filter fitted over the engine air intake, usually seen on Mk. Vs. Available photographs depict BS342 in what appears to be the standard 1943 high-altitude fighter camouflage (Medium Sea Grey over PRU Blue) with B-style markings (without white or yellow rings).

EN459 'HN-D', 93 Squadron, Capodichino (Naples), Italy, late 1943. This Spitfire, well known from the widely-publicised colour photo taken in North Africa while it was 'ZX-1' of the Skalski's Circus, was later allocated to 93 Squadron in Italy in late 1943. By that time, the Middle Stone areas of its upper camouflage have become totally unsuited to the colours found in the operational area, so the light shade was overpainted with a much darker colour. Although the actual shade is uncertain, Dark Green seems the most likely paint used. This would bring the camouflage to Temperate Land standard, in line with Air Ministry Orders at that time.

A 64 Squadron Spitfire F.IX, coded 'SH-A'. This unit received several of the earliest ex-Mk.VC conversions for operational trials during June 1942, and was the first to complete conversion to the new Mark the following month. The starboard side shows compressor scoop and blower drive fairing similar to those on AB197, but this Spitfire features the fuel cooler and the changed panel lines of the makeshift cowling, in line with BS289. The Malcolm hood and no headrest are noteworthy, as is the absence of camera gun port in the starboard wing root.

Another widely-publicised shot that shows a number of interesting details. BS428, while tested at A&AEE in dive-bombing role, showed all the typical features of a very early Supermarine-production F.IX: the stubby carburettor air intake without a filter, the teardrop fairing over the cabin blower drive, the tiny fairings above the rear exhaust stacks (both sides of the cowling) and (not visible here) the wide blister fairings over cannon bays. The small opening on the side of the cowling, well aft and slightly below the cabin blower drive gear fairing, was the coolant header tank relief valve vent. Its low position here is typical for an aeroplane with a Merlin 61 engine. The other small outlet, located at the bottom edge of the top cowling well aft of the exhaust stacks, was the intercooler header tank vent. Retaining squadron markings was not unusual on aircraft tested at Boscombe Down. The codes on this Spitfire are those of 402 Squadron RCAF, one of the first units to have been equipped with Mk.IXs. Following the tests BS428 returned to another Canadian squadron, and then continued to serve with a number of units until scrapped in 1946. Although this F.IX was fitted with the experimental under-fuselage bomb rack as early as February 1943, it was not until the advent of the LF.IX that operational Mk.IX aircraft were used as fighter-bombers.

AB196, the first Spitfire VC converted to Mk.IX by Rolls-Royce at Hucknall. The port ‘bump’ over the intercooler is visible in this shot. It seems that the fuel cooler had not been fitted at the time this photo was taken, as there is no intake in the port wing root leading edge. Being a trials machine, this Spitfire retained the four-cannon armament. After prolonged testing, AB196 was allocated for squadron use during summer 1943, and then served with a number of units until struck off charge in July 1944.

Typical mottle of Spitfire versions and colour schemes at an Italian airfield, probably Foggia, in 1944. 'GZ-M' (JF404) was a Spitfire VIII, while 'GZ-B' (MA631) and 'GZ-D' (probably MA802) were F.IXs. Both 'GZ-M' and 'GZ-B' were in Day Fighter (High Flying) Scheme of Medium Sea Grey on all upper surfaces, with PRU Blue undersides, marked with 'B' type national markings. 'GZ-D', on the other hand, was in standard Day Fighter scheme of Ocean Grey and Dark Green, with Medium Sea Grey bottom, and even with the Sky band around the rear fuselage. Not unusually for the Italian theatre, however, the codes on this Spitfire seem to be red or yellow, rather than Sky, and the propeller spinner is in a darker colour, too.

ENS68 one the initial batch of pre-production LF.IXs, converted by Rolls-Royce from Supermarine-built Mk. VC airframes, was the personal mount of Wg Cdr Al Deere, OC Biggin Hill Wing, during summer 1943. Whilst flying this Spitfire he was credited with an Fw 190 damaged on June 10, another destroyed on June 23, and yet another probable on July 14. Wg Cdr Deere seems to have been specially attracted by Rolls-Royce converted Mk.IXs, having previously scored in F.IXs BS556 (ex-Supermarine built Mk.VC airframe) and JK769 (ex-CBAF Mk.VC). In common with the late F.IX conversions, EN568 had no Aero-Vee filter and featured a standard Supermarine-style cowling with the panel joint line across the bottom section, immediately aft of the third fastener. Another item shared with Supermarine F.IXs was the fuselage roundel in the aft position. The limited green area on the side of the cowling, not reaching further forward than the oil filler cover, was typical for Rolls-Royce converted Spitfire IXs. Note the extremely worn finish of this aeroplane, with the huge amount of exhaust residue along the fuselage.

An informal snapshot of 1st Officer Anna Leska (a Polish ferry pilot) taken at Northolt during summer 1943. The Spitfire in the background clearly displays both the fuel cooler intake in the port wing root, and the camera gun port in the starboard one.

Merlin 61 installation in an F.IX. It was the cabin blower drive housing, visible immediately aft of the propeller, that required the tear-drop fairing on the starboard cowling. The presence of the drive gear along the side of the engine resulted in the coolant header tank relief valve vent outlet being located rather low in this installation. Note the shape of the oil tank.

'Skalski's Circus' about to scramble in late April 1943, with EN315 'ZX-6' in the foreground. Note that outer cannon stubs on this Spitfire lacked the usual blunt fairings. Interestingly, sister ship EN314, which never left Britain, displayed the same flat outer stubs. Curiously, it is hard to discern any disruptive camouflage pattern on EN315, the prominent spill on the main fuel tank cover being the most distinctive patch of a different shade. It is unlikely that the camouflage colours were so faded and worn after merely a month's service. Neither can the strange shades be attributed to lighting conditions or photographic material, as the next Spitfire in line shows the standard camouflage quite clearly. In fact, the apparent lack of contrast between colours on the upper surfaces and the much lighter bottom colour on EN315 correspond to the tones seen in some monochrome photos of Temperate Land/Sky combination. Was this one of those Mk.IXs used in the Mediterranean in such a scheme? Whatever her colours, EN315 was flown by virtually every member of the Polish flight, and was used to score six kills, two probables and two damaged in the hands of five different pilots.

A typical early Supermarine-built Spitfire IX. The unmodified tailplane/elevator and rectangular rear-view mirror were common to all aircraft of this variant from the parent makers. Double blister covers on wing cannon bays were fitted to most Mk.IXs from Supermarine, as well as to early F.IXs from Castle Bromwich. Two tiny fairings on both edges of the top cowling above the exhaust stacks, peculiar to early Supermarine-built F.IXs in the BR and BS range can just be made out. This particular Spitfire, BS459 UZ-T of 306 (Polish) Squadron at Northolt, featured in a series of photos taken with 306 Squadron pilots in late 1942. This aeroplane was lost on January 26, 1943, killing the pilot, in a collision with another Mk.IX, the latter flown by Wg Cdr Stefan Janus, OC Northolt Wing, who consequently became a PoW.

The cockpit of a 316 Squadron Spitfire F.IX receives the attention of groundcrew. The CBAF provenance of this aeroplane is betrayed by no less than three elements of the finish: the camouflage pattern on the nose, the way the warning note has been applied inside the cockpit door, and the position of the fuselage roundel relative to the radio hatch and the IFF socket inlet.

Another Spitfire from the same batch as BR138, BR143 ‘SZ-Q’ of 316 (Polish) Squadron RAF, being refuelled at Northolt in the spring of 1943. Note the cowling 'bump' behind the ground crew. The reinforcing bars over the wheel well have usually been only associated with 'A' and 'B' wings, but the large double blister over the cannon bay leaves no doubt as to the identity of the 'C' wing here. This Spitfire suffered an accident in April 1943, and the round rear-view mirror was probably fitted during repair, as there is an earlier photograph of this aeroplane with the older rectangular one.

Lt John Fawcett of 309th Fighter Squadron 31st Fighter Group USAAF and his Spitfire F.IX MH894 'WX-JJ', named 'Lady Ellen III' after the pilot's wife. The aircraft was one of the very last F.IXs manufactured, but still had the original air intake without the Vokes Aero-Vee, so the Americans fitted the simple filter developed by their maintenance men. Although the finish (Day Fighter scheme with Medium Sea Grey undersides) was neither fresh nor clean when the photo was taken, the CBAF-style camouflage pattern on the nose is evident. The white rectangle under the windscreen was the typical USAAF panel containing the names of the pilot and his ground crew.

MA706 of 318 (Polish) Squadron in Northern Italy during winter 1944/1945 is a more or less typical example of an F.IX at the end of the war. The Vokes Aero-Vee filter and the late-style IFF aerial under the port wing are probably both retro-fits. The redesigned elevator with enlarged horn balance had most likely been fitted to this Spitfire at the factory, but had it not, by that time it might have been retrofitted, anyway. This particular aircraft had the stub outer cannon fairings removed and faired over, to obtain a smooth wing leading edge. Judging by the fact that the Sky fuselage band and the yellow strip along the wing leading edge have been retained, this Spitfire must have been left in the Day Fighter painting scheme, even though the contrast between upper surface colours seems rather low in the poor winter light. Note what appears to be a white ring surrounding the base of the propeller. In accordance with theatre regulations, the spinner was to be red. In most cases only the easily removable spinner cone was repainted, while the backplate of the propeller hub was usually left in the factory-applied Sky finish. To repaint this narrow portion as well one would have to either carefully mask the forward engine cowling, or disassemble the entire propeller! The FK-coded Spitfire in the background is a mystery. Officially this code was assigned to 219 Squadron which at that time flew Mosquitoes over Western Europe!

Sqn Ldr Kazimierz Rutkowski, OC 306 (Polish) Squadron, photographed in front of a unit Spitfire F.IX, most probably EN128 'UZ-N', in January 1943 at Northolt. This picture shows to advantage the standard Supermarine panel joint line across the bottom cowling immediately aft of the third fastener, where two metal sheets were riveted together. The fuel cooler intake is also clearly shown. Note the distinctive exhaust residue on the side of the fuselage. It would be interesting to hear from Merlin specialists about the reasons of such marked discolorations on many early Spitfire IXs.

Photographed in January 1945 at Coltishall, this 303 Squadron Spitfire, featuring Vokes Aero-Vee filter, standard cowling, enlarged horn-balance elevators, and IFF aerial under the starboard wing, could easily pass for an LF.IX or HF.IX, if not for the unmistakable fuel cooler air intake in the port wing root. This F.IX is believed to be EN367, a Supermarine-built Mk.VC converted by Rolls-Royce at Hucknall. Interestingly, the Spitfire still retained the original rectangular rear-view mirror by that time. The disruptive camouflage pattern included a very light shade of grey. The colour layout on the port engine cowling looks typical for a Rolls-Royce converted F.IX.

Another Spitfire F.IX at Northolt, this time MA304 'RF-H' of 303 Squadron in June 1943. Note that this CBAF-built aeroplane featured the later, single-blister cannon bay covers, but retained the older-style horizontal tail surfaces. The 'hump' on the engine cowling is prominent in this view.

The Merlin 63 featured no cabin blower drive gear, so no fairing was needed and the coolant vent outlet was positioned somewhat higher. Note the different style of oil tank in this photo

AB197, the other of the two original Mk.IXs, during trials in early 1942, also with a black spinner. In these earliest conversions virtually every panel of the original Mk.V cowling was used, including the two bottom elements. The starboard 'bump' on the top cowling had the Heywood compressor air scoop on top of it, which gave it an even more bizarre appearance than the other one. Note the tear-drop shaped fairing over the cabin blower drive housing, on the side of the cowling immediately behind the propeller. Another noteworthy feature is the slant panel line between the fuel tank cover and the engine cowling. As shown here, this Spitfire did not carry the outer cannon, and such a configuration would become standard on all F.IXs. Unlike AB196, this Spitfire spent her entire life as a trials aircraft.

Delivered from Eastleigh on June 10, 1942, BR592 was the second Mk.IX converted from a Mk.VC by Supermarine rather than by Rolls-Royce. This Spitfire was one of the initial batch delivered to 64 Squadron during late June/early July 1942. She was lost to Fw 190s on October 11, 1942, still with the same unit. This photo reveals the difference in the nose area, as compared to that of BS289. The Supermarine conversion cowling was much neater than the makeshift Rolls-Royce variety, and the camouflage pattern in this area was entirely different. Note the two small blister fairings on the side of the upper cowling that betray this panel as a modified Mk.V item. Similar to BS289 this Spitfire featured the flat-sided cockpit hood and the headrest. The wing leading edge shows no sign of either the machine-gun ports or the fuel cooler air inlet. It seems that the latter item was not introduced until a lesson was learned from engines cutting out during fast climbing on hot summer days.

Fine study of an early Supermarine production F.IX, showing the most prominent features that distinguished this version from the Mk.V: the four-blade propeller and the rectangular radiator under the port wing. Note the fuel cooler intake in the port wing root leading edge and the absence of camera gun in the starboard wing root. The underfuselage conformal fuel tank was essential for Mk.IX operations over the Continent. This widely-publicised photo is one of a series taken in late 1942 of 611 (West Lancashire) Squadron, one of the first units to convert to Spitfire IXs. The officer on the wing is Flt Lt William Vernon Crawford-Compton, a New Zealander who scored most of his 20 victories flying Spitfire IXs. During his time with 611 Squadron he achieved most success in BR632, one of the earliest Rolls-Royce converted Mk.IXs.

Richard Beall of 421 Squadron RCAF pictured in mid-1943 by his usual mount, BR138 'AU-G' 'Skychief II'. Before being allocated for squadron use, this Spitfire had been used for comparison trials with AB196 at RAE Farnborough. Note the distinctive bump on top of the cowling, the non-standard panel lines, and the unusual shape of the oil filler cover immediately forward of the 'Red Indian' emblem. This photograph, published by Robert Bracken in his 'Spitfire: The Canadians', triggered a dispute on the early Mk.IX conversions, leading to this article.

By late 1943 EN459, previously the 'ZX-1' of 'Skalski's Circus', had become 'HN-D' of 93 Squadron. On October 15, 1943, Flt Lt 'Hap' Kennedy used this Spitfire to down a Bf 109 in Italy. By the time this photograph was taken, Middle Stone areas of the Desert camouflage were repainted with dark colour. Dark Green seems the most likely hypothesis, turning the scheme into regulation Temperate Land.

Not a very clear photo, but an extremely interesting one. It shows an F.IX fitted with both the high-altitude pointed wingtips, and the 'Aboukir'-style tropical filter, originally developed for Mk.Vs. In all probability this is one of the early Mk.IXs introduced in 1943 for high-altitude defence in the Suez Canal zone. The Spitfire seems to sport a rather unusual scheme of a single colour overall. Also the 'B' type roundel and 'C' type fin flash appear rather non-standard, with very light blue portions. This would indicate that the photo was taken using ortho film or a colour filter, which rendered blue shades much lighter than they really were. In fact, the fighter was probably finished in standard Day fighter (High flying) scheme.

Leaving Hucknall in late September 1942, BS289 serves as a perfect example of an early series Rolls-Royce-converted Mk.IX. General cowling lines, the 'bumps', and the camouflage pattern on the nose, are all similar to the prototype conversions. However, the fireproof bulkhead and its corresponding panel lines have no slant any more, and the fuel cooler air inlet is prominent in the port wing root leading edge. Also the bottom panel of the cowling is a brand new part, rather than a modified Mk.V component. Note that BS289 featured the flat-sided cockpit hood and headrest, although both items had been declared obsolete by that time. It looks like this Spitfire was not fitted with the 0.303in machine-guns at all. During late 1942, BS289 was delivered to the Mediterranean as one of the first Mk.IXs in that theatre.

Fg Off Leopold Zakrzewski in front of BR143 'SZ-Q'. Note how the shape of the oil filler cover was different from that on the BR138. Also the bottom cowling fastener forward of this cover was rather unusual. BR143 was lost to Focke-Wulfs on June 17, 1943.

Spitfire F.IX EN173 'RF-C' of 303 (Polish) Squadron photographed during servicing at Northolt on June 24, 1943. The nose looks rather 'humpy', contradicting the widespread notion that such shape of the upper cowl was only associated with later LF.IX aircraft. Note that the bottom of this Spitfire is markedly darker than the upper colour which occupies the place of Ocean Grey. EN173 was lost to Fw 190s on September 24, 1943.

Flt Off Adam Sworniowski (left) with an unidentified pilot in front of a Spitfire F.IX of 315 Squadron, possibly EN171 'PK-C. The aeroplane is in a rather unusual colour scheme, with the bottom painted distinctively darker than one of the upper colours. Had the photo not been taken at a UK-based unit, one could take the scheme to be Desert, with Azure or Light Mediterranean Blue undersides

Fitters of 316 (Polish) Squadron at the starboard wing root of a squadron Spitfire, working on the camera gun.

Pleasant scene at Northolt: Sgt Tadeusz Jankowski with his daughter Haneczka pictured by LZ989 'SZ-J' of 316 Squadron (the aircraft is positively identifiable by the personal emblem under the windscreen). One of the first Mk.IXs to leave the Castle Bromwich Aircraft Factory, this Spitfire shows the two panel joint lines on the nose cowling associated with that maker: one across the bottom between the second and third fasteners, and one across the top above the first exhaust stack. Also the camouflage layout on the nose is very typical for the CBAF production

Ground crew member of 318 (Polish) Squadron working on a Spitfire F.IX. The shape of the standard air intake fairing of this variant, which only remotely resembled that of the Mk.V, is shown to advantage. Note that the fuel cooler inlet in the wing root has been patched over. It is not clear whether this means the cooler unit has been removed, or just unused, as the squadron never operated at high altitudes. No.318 was a fighter-reconnaissance squadron operating in Italy, and typically for that theatre it operated a colourful mix of Spitfire VBs, VCs (some tropicalised), F.IXs, LF.IXs, and even HF.IXs in tactical recce and ground attack roles.

Captain Francis Gabreski leaving the cockpit of a Spitfire F.IX, most probably BS410 'PK-E', during his exchange tour in 315 (Polish) Squadron in early 1943. Note the stencilling 'make sure door is locked before flight', applied in typical Supermarine style, in both upright and inverted positions, in the central section of the cockpit door.

EN459 'ZX-1' of the 'Skalski's Circus' undergoing repair at Gabes in April 1943, following a forced-landing by Flt Lt Horbaczewski. Port wing of the Spitfire, visible in the background, features a double-blister cannon cover. This Mk.IX was originally painted in Day Fighter camouflage at the factory, before wings were matched to the fuselage. Desert colours were not applied until after the Spitfire was assembled, so the bottom of the fuselage still retains grey-and-green colours in the area where they would be covered by the wing root fillet. Note that also the radio aerial mast seems to have been left in Ocean Grey.