WB’s recollection of having seen in the Science Museum a 1795cc 11.9hp Dorman engine (69mm x 120mm) is correct. It was there before 1937 until about 1960, and its position in the exhibits was then taken by a Riley 9 engine!
Another example of this engine was an exhibit in the engineering laboratories of the University of Oxford (Nexham Gardens). This was there in 1943 and may well still be there today. However an example is still on the road in the blue Laere road-sweeper which took part in the Historic Commercial Vehicle Brighton Run in May last year. Incidentally, the later Laere sweeper (which was also present at Brighton) had a Meadows engine (compare Frazer Nash and Lea-Francis engines)!
One light-car which employed this Dorman engine was the 1923 12hp Vulcan. From 1926 to 1934 I serviced and in later years drove one of these cars. During this time the only thing that ever went wrong with the engine or indeed the car was that the magneto required remagnetising once. The engine was remarkably smooth and quiet (far quieter than the average Riley 9 engine) and the fuel consumption was over 30 mpg.
Roger Hargreaves, Reigate, Surrey