Over fifty years ago, main line steam in Britain ceased to exist: the last 'official' date was 11 August 1968. At the time, British Railways' plan was that this was to be the end of steam traction - although a special dispensation was given for Britannia Class 4-6-2 No. 70013 Oliver Cromwell to travel under its own steam into preservation on the 12th and 13th of that month. We now know that this was not quite the end; that, in fact,...