Not rain, but fog! I was at Crewe in 1969 when their meeting with Long Eaton was abandoned after seven heats.
Perhaps on a smaller track they could have carried on???!!!
For me, the World Individual Championship ran from 1936 to 1994. Before then there were various other events, 1940-48 too. From 1995, there’s been a Grand Prix Series, with its own champion.
Somewhere else that’s closed is Jack’s Hill Cafe on the A5 to the north of Towcester. This was a regular stop for supporters’ coaches returning north from the big meetings at Wembley, also in the London area such as British Finals, FIM Internationale, etc.