eyebrow

yea he wasn't wearing his seatbelt so he hit the dashboard and it moved his eyebrow up 3 inches.

At first glance I thought it was botched surgery for a drooping eyelid, but there's no scar and looking at some more photos I see that it isn't always up. There are pictures of him with a completely smooth, relaxed brow. So it's definitely something muscular going on, whether he's doing it on purpose or not I don't know, you'd have to ask him. Maybe he's a fan of The Rock. ;P

When he raises it? I don't know but i like it a lot :)

i've actualy noticed it on a lot of UK actors. David Tennant included. I wonder if it's some sort of tick running through a few gene lines.

bcastcult.com

In some article he mentions that as a boy he was in an accident with his brother, Damian. They were sledding or some such thing & they went into a fence. He sustained injuries to his face. I assumed the eyebrow thing came from that... but maybe not.

Whatever the cause, it does look like he's had damage to his face & surgery to repair it.