One-hundred-and-eighteen M15s and all thirty-two M15rs (including numbers 789 and 790, the two locomotives that were rebuilt with GER Class G69 cabs), passed into London and North Eastern Railway (LNER) ownership at the 1923 grouping.

They were then deployed on armoured trains, not only in their native East Anglia (Westerfield, Mistley and Tilbury), but in Kent, Lincolnshire and as far north as Aberdeen.

They were also found at Ministry of Defence depots in the west of the country (Bicester, Long Marston and Wooton Dassett.

Their BR numbers were: Ten of the original series of forty engines constructed between 1884-87 were withdrawn in Great Eastern days, between September 1913 and December 1922.

The completed locomotive (originally set to appear as 67218 in BR Black) is to be outshopped as No.789 in Great Eastern Railway blue livery.