This Merlin 61-engined Mustang was one of a number of interesting aircraft flown by the Rolls-Royce Test Establishment at Hucknall.

The first Rolls-Royce Mustang X conversion, with Merlin 65 installation.

The first Rolls-Royce Mustang X conversion, with Merlin 65 installation and with the nose intake lines revised after early flight testing.

One of the other Rolls-Royce conversions of P-51s to Mustang X configuration - AM203.

One of several Mustang Xs produced by Rolls-Royce, with Merlin 61 or 65 engines. This example, AC963, has a dorsal fin.

Пять опытных самолетов с улучшенной силовой установкой Merlin 65 получили обозначение Mustang X. Прототип N'2, бортовой номер AM203, с более обтекаемым воздухозаборником в передней части фюзеляжа и расположенными под углом к капоту отверстиями для охлаждающего воздуха развивал на высоте 6811 м скорость 679 км/ч.
One of the other Rolls-Royce conversions of P-51s to Mustang X configuration - AM208.

Mustang I AM208 was one of those used experimentally at Hucknall and the A&AEE, Boscombe Down. Apparent here is the 'chin' radiator, although the ventral radiator remains unchanged.