Couldn't see anything reason when I changed the wheel but going to the tyre monkeys later today so will see what occurred. I'm guessing the tyre is toast as it lost pressure like it'd been slashed.
Turns out there was a clean cut right through the tread about the length of a Stanley knife blade. Nice. Also turns out I had a lifetime warranty on the tyres that I knew nothing about so got a new one for free. Which actually is nice.