"For the first time in more than 100 years, a steam train was carrying passengers on the Tube yesterday."
This part of the story is slightly misleading. Steam haulage on the London Underground still existed until September 1961. Up to then the Metropolitan Line extended to Aylesbury. Electric locomotives hauled trains as far as Rickmansworth and there a steam loco took over to take the train on to Aylesbury. By September 1961 the line had been electrified as far as Amersham and on September 10th the last steam train ran through to Aylesbury. I was on that train and I still have my ticket. After that the service was taken over by conventional electric multiple unit trains (of a type, coincidentally, that was withdrawn earlier this year) and the Underground service was truncated back to Amersham.
Although not passenger carrying, steam hauled maintenance trains still ran on the Underground from Lillie Bridge (Fulham) and Neasden depots. These trains ran through some of the tunnel sections and they continued until the mid 1970s.