Former bartender Justin Theroux often takes over cocktails at celebrity friends' parties - because the hired staff don't know how to serve perfect tipples.

The Wanderlust star, who is engaged to Hollywood party favourite Jennifer Aniston, became a top bar man as a young actor and he admits the skills and expertise he learned back in the day have stayed with him - and he never wastes an opportunity to give party guests the best drinks.

He says, "People like their drinks a certain way and then sometimes they're not made properly and I can't help but get behind the bar.

"Vodka should be frozen and usually it's not and it melts the ice... and it's a party and they're (bar staff) cheap and they're slicing the limes up really thin,so there's not enough lime. I'm a control freak that way."