Revelling in the magic of parenthood, it's Professor Dumbledad

Late fatherhood seems to agree with notoriously grumpy actor Sir Michael Gambon - pictured for the first time with girlfriend Philippa Hart and their newborn baby enjoying the sunshine.

The 66-year-old Harry Potter star and the 42-year-old designer reclined on a bench to coo over their new addition, who was born a fortnight ago, after taking a stroll through a West London park.

Wearing sunglasses and an opennecked shirt, and with the lead of his partner's pet pug dog slung around his neck, Sir Michael - known to a generation of children as Professor Dumbledore in the Harry Potter films - appeared relaxed as he chatted to Miss Hart and gazed at the baby.

An onlooker said: "He seemed quite the attentive father, putting a protective arm around his girlfriend as they walked, and checking the pram to make sure the baby was happy."

The infant, whose birth has not yet been registered, is the first born to the legendary thespian and his mistress, with whom he does not share a home.

Notoriously private, the actor has not revealed the name, or even the sex, of the child.

The Dublin-born actor first met Miss Hart seven years ago on the set of the film Longitude, in which he played an 18th Century clockmaker on a life-long quest to measure longitude.

He introduced her as his girlfriend to Gosford Park co-stars including Charles Dance and Dame Maggie Smith in 2001.

But he remains married to his wife Anne, with whom he has a son only slightly younger than Miss Hart.

The couple live separate lives, with Lady Gambon remaining at the family's £4million marital home in Kent after Sir Michael moved into a bachelor pad.

They are thought not to have divorced due to their Roman Catholic faith.

The multi-Bafta-winning actor, who was knighted in 1998 for services to theatre, has appeared in three Harry Potter instalments since taking over the role of Hogwarts' headmaster from fellow Irish actor the late Richard Harris in 2004.