Sir Paul McCartney has become a father again at the age of 61 after his wife Heather Mills gave birth to a baby girl two weeks early.

They have named the child Beatrice.

Her delighted father Mark told of his joy today and hoped the delivery of his first grandchild would help build bridges with his estranged daughter.

She gave birth yesterday at a north London hospital close to the couple's home in St John's Wood.

Sir Paul already has three children from his marriage to Linda, who died in 1998 - musician James, 25, photographer Mary, 33, and fashion designer Stella, 31.

He also has a stepdaughter, Heather, from Linda's first marriage.

The child was delivered yesterday at the Hospital of St John and St Elizabeth in London, close to Abbey Road where The Beatles recorded most of their magical moments.

There has been no official confirmation so far but a statement is expected to be made outside the hospital shortly after 11am.

''I am very proud of my daughter and what she has achieved.''

Sir Paul, 61, married anti-landmine campaigner Heather in June 2002 in a ceremony at an Irish castle.

But they had feared they would be unable to have a child together because of complications when Ms Mills was younger.

She suffered two ectopic pregnancies a number of years before meeting Sir Paul, during her marriage to computer sales director Alfie Karmal. They split in 1989.

Ms Mills, a former model who lost her leg when she was hit by a police motorcyclist on an emergency call, now devotes much of her time to anti-landmine campaigning.

Mills recently described the tearful moment when she revealed she was carrying their longed-for child.

She told US chat host Larry King: ''I showed him the test and he just went 'Oh'. We both started crying and it was just a miracle.''

Just three months earlier she had told TV interviewer Michael Parkinson that there was little chance she would be able to conceive. Earlier this year she spoke about how she thought she might never conceive again.

''The chances of me getting pregnant are about that much,'' she said, holding her thumb and finger an inch apart.

''And I'm sure for any woman out there it's hard enough when your family keeps saying 'When are you going to have a baby, then?' - never mind the whole world keeps saying 'Oh, she's pregnant this week'.''

The couple had kept the sex of the child secret, although they had already named it. Mr Mills, speaking at his flat on the outskirts of Washington, Tyne and Wear, said today: ''This is my first one and it is a grand time for me and I love the new baby. ''I sincerely hope the baby will bring us together again.'' He said he was told last night by a friend that she had gone to hospital. He has not spoken to Heather about the birth. The couple's last public appearance was at the UK premiere screening of a tribute concert for George Harrison in London earlier this month. She wore a long burgundy crushed velvet gown which showed off her bump.