Brad Pitt admits looking after six children is tougher than starring in action movies.

The Hollywood heartthrob - who raises, Maddox, 11, Pax, nine, Zahara, seven, Shiloh, six, and four-year-old twins Knox and Vivienne, with fiancee Angelina Jolie - gets a lot more bruises being hands-on father than he ever did doing the stunts for new film 'Killing Them Softly'.

He said: "Does it ache? Sure. The knees have gone, the back is crunchy.

"Getting the kids ready for school is every bit as painful as anything I had to do in this film."

Brad and Angelina are in the process of organising their wedding but he admits best friend George Clooney won't be his best man because "he doesn't believe in institutions".

However, Brad has confessed they haven't set a date yet, even though the children are pressuring them to do it, and could tie the knot in the UK, after spending the summer in London.

He said: "We are going to do it. We haven't set a date yet, though. We are getting a lot of pressure from our kids.

"We could do it in the UK. It has been such an amazing summer here, with all your events - the Jubilee and the Olympics. I've watched everything."