Matt Parker's video: https://www.youtube.com/watch?v=b9OEuhdM6t8 Geoff Marshall's behind-the-scenes video: https://www.youtube.com/watch?v=IIMbF_Amuc4 Beautiful diagrams of tube platform heights: https://www.dansilva.co.uk/down-underground Sabetta Matsumoto and I went to check that the knot we made on the tube (with Matt Parker, Geoff Marshall and Vicki Pipe) was actually the left-handed trefoil, and not some other knot.