The Brunel Engineering Centre Trust, under a Manpower Services Commission (MS) scheme, completely dismantled 6023 and restoration began.

6023 was then bought by the Great Western Society (GWS) and moved to the Didcot Railway Centre in March 1990 for its restoration to continue.

All "Kings" had been converted to double chimneys under British Railways ownership, which improved performance and efficiency but changed the original appearance.

The locomotive re-entered passenger service on the Mid-Norfolk Railway on 4 June 2011, as part of a running-in programme leading to the engine's return to the main line.

[5] During the road journey to Dereham, the locomotive lost its safety valve cover, with the Mid-Norfolk offering a cash reward for its safe return.

[7][8] The locomotive then made a series of appearances on the Great Central Railway, for both testing and running-in purposes but was later returned to Didcot where it was to be prepared to operate on the main line.

[9] The only mainline journey it undertook, was to be hauled in light steam by 70013 Oliver Cromwell to a display at Old Oak Common TMD via London Paddington in August 2017.