Before the final British Railways scheme for mixed traffic locomotives was chosen, four Black 5s were taken into Crewe Works during January 1948 and repainted in various experimental liveries. 4762 had Southern Railway malachite green, lined yellow and black, 4763 had LNER green, lined black and white, and 4764 was in GWR green, lined orange and black; the fourth, 5292, was in black, with grey/cream/red lining in LNWR style. 4763, 4764 and 5292 had 12” LMS 1946 pattern plain white numbers on the cab sides whereas those on the left hand side of 4762 were in Southern Railway style, shaded yellow. There were 6” letter Ms halfway between the numbers and the cab windows, and 2” power classification 5s below the numbers. BRITISH RAILWAYS was painted on the tender sides in 8¾” sans serif letters.
The four were then paraded before the ‘top brass’ at Addison Road, Kensington on 30 January 1948 where 4762 is pictured. After the display the engines were returned to Crewe and lining was added to their right-hand sides.