The Signalman Who Forgot One Train

For two and a half years, two signalmen at a quiet box on the Scottish border had been secretly cheating the start of their shift, covering it up by faking the train logbook. On the morning of 22 May 1915, buried in the backlog that scheme created, one of them forgot that a train was parked on the main line — right outside the window — and let another one onto the same track. Officially, 227 people died. Most accounts round that down to 226. The honest truth is that nobody will ever know the real number, because the list of who was even on board burned in the same fire that killed them. Britain already had a rule, decades old, built to make this impossible. It had a machine built to make it physically impossible, too. And it had one small object, meant to catch the exact thing the machine couldn't see, that simply wasn't there that morning. This is how absolute block signalling, mechanical interlocking, and the lever collar actually work — and how, layer by layer, that same idea got automated into the system running underneath almost every train in Britain today, including the one time, in 1999, it very nearly failed again. Sources are pinned in the comments. Where a figure is derived, an estimate, or our own arithmetic, it says so on screen. CHAPTERS 0:00 A signal box, 6:49am 1:57 The title 2:00 The collision 2:51 227, officially 3:29 The trial 3:58 There was already a rule 5:38 The lever frame 6:42 The collar that wasn't there 7:23 Three layers 7:47 How machines watch the track now 9:16 TPWS, and where it can't reach 10:09 Ladbroke Grove, 1999 11:37 The newest layer 12:02 Back to that morning 12:40 Next episode THE BORING MACHINE How the machine actually works. New episode every other Tuesday. Business enquiries: sponsors@theboringmachine.tv #howitworks #engineering #railways