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Transport for London has released hundreds of historic documents into Google's cultural archives. And, wow... there's a lot of stuff.
TfL's new presence on Google Arts & Culture is absolutely worth an hour of your time. Over 2,000 images and documents have been uploaded, many of which you probably haven't seen before (I certainly hadn't, and I've spent many years obsessing over this stuff). We're talking maps, photos, diagrams, wartime memories... it's a transport treasure trove.
If you're just after a bit of a play, then a good place to start is the "Choose your line" section up top. This presents a highly visual chronology of each tube line (plus Elizabeth line and the not-yet-split-up Overground), illustrated with maps, diagrams and photos.
I'd also recommend taking a look at the '10 Map Tales' story, which includes one or two charts I'm betting you haven't seen before, such as a hand-drawn 'star' map as a proof-of-concept for mapping bus routes.
There's a ton of other stuff on there, including maps from the 1937 and 1953 coronations, pictures of famous people riding the tube, behind-the-scenes at the lost property office and even a crossword from "a 1949 TfL staff magazine" (quite a coup, given that TfL wouldn't exist for another 51 years!).
The material is drawn from TfL's Corporate Archives, and we're promised it will be "regularly updated" with new deposits. This being Google Arts and Culture, the images are presented within 'stories' rather than in a more structured format. It's a site geared up more for casual browsing and rabbit-holery, rather than a place you'd come to look something up. And, the odd anachronism aside, it's very well done. Go have a play.