I didn't say have a plan in place for everything, but at very least have considered the top 10 things that could stop the show. After 'major terrorist attack the day/week before', 'UK weather' should not have been much higher up the list, especially in view of the floods last year which had a major impact on local areas. Volcanos, locust swarms and alien invasion would have been really unforeseen - crap UK weather isn't gobsmacking.
I'll reiterate, I feel very sorry for the organisers and am certainly sat here with the benefit of hindsight, but to be perfectly frank, I would have considered all sorts of options if I was organising, just as I have done at lesser events that I've chaired. I'm not saying I could have done better, or that necessarily anything practical could have been done, but I'd have looked at it before last week.