(rebuilt), the B12/3 (re-boilered and new valve gear) and his K4 (built for the West Highland Line) and P2 (for the Aberdeen to Edinburgh route). Thompson, having spent a time introducing a conveyor system into the stores at York and Doncaster, was an advocate of a small variety of classes, and spent time during his tenure as CME in developing a list of classes either rebuilt to his standard (like the B2, A2/2, K1/1 etc.) or built new to standard designs (the B1, L1 etc.). The standardisation centred largely around the B1 boiler, which had been developed from that on the B17, 20" cylinders (a layover from the original A1 class's outside cylinders/K2 Cylinders, but with 10" piston valves), and a range of standard wheel sizes (among them 5 ft 8 in, 6 ft 2 in and 6 ft 8 in). A number of intermediate 4-6-0 classes, such as the B16, B17 and GCR types, were rebuilt into outside-cylindered classes, where wheel size was the only major varying detail. The programme had the desired effect of reducing the variety of LNER classes, and allowed the withdrawal of a number of worn-out pre-grouping classes, but a good many of the rebuilds and in fact the new builds had design flaws, so that the problems Thompson solved for the Maintenance Dept. were replaced by new ones for the Operating Dept. Thompson's designs Pacific rebuilds Thompson criticised many of Gresley's practices, but equivalent comment can be made about many of Thompson's designs. Upon taking up his post, Thompson tried to convince the LNER hierarchy of the need to rebuild the Gresley Pacific and Mikado classes. The Directors of the LNER, having witnessed a Gresley A4 take the World Speed Record for steam, were sceptical about this, so Thompson researched as many middle big-end bearing failures on the LNER as he could find, attributing them to the design of the conjugated motion, even garnering outside opinion from the LMS. Despite roundly criticizing the Gresley motion, his Pacific rebuilds were not the best designs. They retained three cylinders, but with divided drive and 3 independent sets of Walschaerts valve gear. Thompson attached great importance to having the connecting rods equal in length, which was in fact unnecessary. As a result, the outside cylinders were placed behind the front bogie with the inside cylinder well forward. This gave the engine an unnecessarily long wheelbase, created long