The almost impossible chessboard puzzle

Check out the meta-solution on 3Blue1Brown: Thanks to Gordon' s Wine Bar for letting us film in their bar. Ha! It wasn't a dungeon, it was a wine bar all along! (An amazing wine bar at that; definitely visit it next time you're in London (and things are open again)). Also: this was filmed back in February 2020 pre-coronavirus (at least before we knew about it). Which is why we're sat so close together and not wearing masks. And people are phoning a wine bar. For those of you want it all, and you want it now, we've put the complete, unedited footage of Matt and Grant completing the puzzle scenario on Matt's second channel. We'll put the deleted footage on the Stand-up Maths patreon page: Sorry the audio is a bit hit and miss. Matt's microphone dropped out for a bit so we tried