Arthur Darvill, who plays Rory in Doctor Who, is the last Tooth Guard before the door leading to the Tooth Fairy's door. He isn't credited on imdb. Fun little cameo! It seems like 90% of British actors have appeared on Doctor Who at some point.
shareMuch as I would love to see Arthur Darvill in a 'Discworld' adaptation, I'm fairly sure the one you're referring to is Tim Plester ('Toothguard 7'). He does bear a striking resemblance to Arthur, though, I'll admit - I thought it was him, too, at first!
shareIt seems like 90% of British actors have appeared on Doctor Who at some point.