Brad Pitt has a big problem chatting to his six kids about Santa Claus - because he was devastated when he discovered his own parents had been lying to him about the man in the big red suit when he was a child.

The movie star's children with Angelina Jolie were spotted delivering letters to Father Christmas in Kent, England last month (Nov12), and Pitt can only hope they'll forgive him and their mum when they realise the truth about Santa.

He explains, "I'm not real big on the whole Santa thing. I thought it was a huge act of betrayal when I was a kid. I didn't like that. When I found out the truth, I was like, 'Why? Why? Why would you lie to me? Why?'"

But he's not about to ruin Maddox, Pax, Zahara, Shiloh, Knox and Vivienne's holidays: "I tell them that some people believe it's Santa, and some people believe it's parents (who put your gifts out), and you get to believe whatever you want."