The identity of the train robber who assaulted Mills has been the subject of some debate, but most sources agree that Mills' assailant was one of three members of the gang who were never identified. He was referred to as "Mr Three" by Ronnie Biggs, and "Alf Thomas" by Piers Paul Read and Bruce Reynolds. Where all accounts agree, is that Gordon Goody made Mills drive the train after the failure of the robbers' substitute driver, and that Charlie Wilson told Mills not to worry and that he would not be harmed and ensured he was left alone after that. Williams (at the time a retired Detective Chief Superintendent) claims in his 1973 book "No Fixed Address":