Can I delete gazillions of pending comments at once?

Just came back to an old blog and found over 42,000 spam comments pending. I’ve now activated Akismet — that’s called shutting the stable door after the horse has bolted!

Anyway, I can only see how to select and delete 20 at a time. Is there any way to select all 42,000 and delete them all at once?

Otherwise I’ll be hear for a month deleting!