What happened to Oliver's hair?

I've just re-watched this film. (I was bored and there was nothing on tv) I still think Tim Roth was a terrible choice as Cromwell. Too small, too violent and not enough hair! It's not as if there aren't one or two portraits of Cromwell! He had long hair! I know a lot of the soldiers didn't hence 'roundheads' but Ollie did!

Waiting for my Mr Colin Firth Darcy