High Quality Content by WIKIPEDIA articles! Allen William Mark (Doc) Coombs (23 October 1911 – 30 January 1995) was a British electronics engineer at the Post Office Research Station, Dollis Hill. He was one of the principal designers of the Mark II or production version of the Colossus computer used at Bletchley Park for codebreaking in World War II, and took over leadership of the project when Tommy Flowers moved on to other projects.