With the unexpected death in office of Sir Nigel Gresley, the LNER appointed Thompson his successor as chief mechanical engineer who in 1945 produced the first drawings for a rebuild of the three cylinder K4's into a two cylinder engine, fitted with the tender Thompson had designed for the B1. The first rebuild was completed in 1946 and, after trials, the K1 (as it had become) was deemed a useful successor to the old J39 0-6-0 tender engine and could match the B1's in most areas, pulling everything from coal freight to express passenger services. Thompson retired the following year, leaving Peppercorn to make further modifications to the design, including fitting a larger tender - in total 70 examples were built, the last being withdrawn in 1967. 62005 survives in preservation.
This engine was built by a professional engine over a period of ten years, using Don Young drawings and castings. Extensive use was made of drawings and photographs taken from the full size engine.
Superheated boiler fed by twin injectors, copper silver-soldered construction. Piston valve cylinders with Walschaert's valve gear, cab-operated drain cocks. Painted and lined out in British Railways black livery, the paintwork has been well done and is in good condition.
In addition to a complete set of drawings, there is a quantity of good large black and white photographs showing details and the builders notes made at the time, along with its past boiler certificates. The current certificate expires in 2004.