When do Hedgehogs Start Hibernating?

He phoned the BBC and asked to be put through to his department head.“Oh, hello, Arthur Dent here. Look, sorry I haven’t been in [the office] for six months but I’ve gone mad.”“Oh, not to worry. Thought it was probably something like that. Happens here all the time. How soon can we expect you?”“When do hedgehogs start hibernating?”“Sometime in Spring, I think.”“I’ll be in shortly after that.”— So