Itsfab I don't think it was arson after all. I've heard it was faulty cabling on a machine in the arcades. (No idea if that's reliable though, it's just what I've heard.)
But anyway, 3pm in the afternoon on a summer's day would be an odd time to start a fire on the pier don't you think? Eastbourne Pier, and the arcade in particular would have been packed with people. Arsonists much more likely to strike in secret e.g. at night, don't you think?