It Could be any married couple playing happily with their son.

Star Brad Pitt gives actress Angelina Jolie's four-year-old son Maddox a lesson in dirt-track biking.

Angelina looks on as they romp around the paddock in the sun, surrounded by wild flowers.

This intimate portrait of family life is certain to fuel suggestions that, despite their protestations, Brad and Angelina are romantically involved. Both have furiously denied they have ever been anything other than close colleagues

Brad, 41, spent some time with the son of his Mr And Mrs Smith co-star not far from Angelina's home in Buckinghamshire.

Wearing only shorts, socks and trainers, bleach-blond Brad looked tanned and relaxed - as did Angelina in black trousers, top and flip-flops.

Close bond A close friend of the couple, who was there at the time, said: "The bond that is developing between Brad and Maddox is delightful to see. They spend a lot of time playing together and I'm not sure who enjoys their games more.

"Maddox is so so precious to Angelina. She is a committed mother and it says much about her feelings for Brad that she trusts him so deeply with her son.

"As protective as she is, she's thrilled to see the little boy having such an exciting time. All three are taking time, building a wonderful, loving relationship. Angelina and Brad are generous people, who give so much to others, and their friends wish them all the happiness in the world."

Brad is not the first father figure for Maddox. Angelina, 29, who is twice-divorced, was also linked to actor Colin Farrell when she appeared with him in Alexander.

Rumours that she had moved on began after Brad announced in January that his marriage to Jennifer Aniston was over after nearly five years. Brad was said to be desperate to have children, while his 36-year-old wife was thought to be keen not to interrupt her career soon after the end of Friends. But almost before divorce papers were served, pictures surfaced of them sharing intimate moments while filming Mr And Mrs Smith.

Just two weeks ago Brad snapped angrily when asked if Angelina had broken up his marriage.