The year-long party to mark the Underground's 150th birthday continues this evening, when BBC2 screens an hour-long documentary, The Tube: An Underground History.
A follow-on from last year's fascinating series The Tube (in which we learnt about the meaning of a Code 2 alert) the new doc continues where its predecessors left of, telling the story of the world's first and most famous subterranean railway through the people who work on it. There will also be footage from some of the network's many abandoned stations.
The Tube: An Underground History is on at 9pm, BBC2 tonight, and will go on iPlayer after that (if you're not in the UK, you're out of luck on both counts). Here's a clip from showing the remains of a Greathead shield (or 'grate head shield' as it's mistakenly captioned), which was used to build the tunnels for the deep-level lines.