I can confirm it was totally unprovoked as I was standing right next to him at the time. It's likely he only went for TOKs is because he's only ickle. I don't think the guy would have been able to reach my head. It wasn't a very nice experience.
The cops were called, but there was not a lot they could do. But we did give a description and the direction he fucked off in, so at least the zillions of cops all over the city that night could be alerted that there is a violent maniac on the loose. If the bloke was that wound up, I don't doubt he'd go looking for more people to head butt.