From the video description:
"The British Library is one of the six legal deposit libraries for the UK — and the only one that doesn’t pick and choose, or have to ask for copies. That’s a lot of books to store, and the internet’s only making it worse. ■ The BL: https://bl.uk ■ UK Web Archive: https://www.webarchive.org.uk/
This video has a correction: it turns out the formal interview requirement for a reader pass has been dropped. However, you’ll still need to get a pass, and you’re not allowed to take books out of the reading rooms! You can see all corrections on the channel here: https://www.tomscott.com/corrections/
"Clickbait title, since that library definitely does not have every book ever published. It doesn’t even have every book ever published in English. But that’s Tom Scott for you.