Prince Harry has declared he is ready to play the proud, protective uncle for his new nephew Prince George and "make sure he has fun".

Harry could not stop beaming as he talked about the newest member of his family during his visit to a photographic exhibition in London documenting the work of his Africa-based charity Sentebale.

Asked what his mission was as an uncle the royal replied: "To make sure he has a good upbringing, and keep him out of harm's way and to make sure he has fun.

"The rest I'll leave to the parents."

The royal said he had already cuddled the Duke and Duchess of Cambridge's baby born on Monday and on Wednesday named by his parents George Alexander Louis - Prince George of Cambridge.

The baby is destined to become George VII if his grandfather, the Prince of Wales, and father, William, choose to use their first names when they become monarchs, and not a middle name.

The infant prince's name is thought to be in tribute to the Queen's father, King George VI.

The 28-year-old prince last night said: "When I saw him he was crying his eyes out like all babies do I suppose - it's fantastic to have another addition to the family.

"I only hope my brother knows how expensive my baby sitting charges are."

Ever the joker when asked what his nephew was like he held up his hands and said: "Well he's about that long and about that wide."

The Prince said it was too early to say whether Prince George takes after any member of the family, as: "He is about four days old so I think you can judge that one for yourself. I've no idea."

And when he was asked whether Prince William was up to the job of fatherhood, he replied: "Of course he is. Hopefully most people are."

The Prince had spent around half an hour viewing the exhibition Sentebale - Stories of Hope at the Getty Images Gallery in central London.

Some of the pictures were taken in February during the royal's trip to the southern African kingdom of Lesotho, where his charity supports a range of projects that help disadvantaged children and young people.

Sentebale, which means Forget Me Not in the local language, was founded in 2006 by Prince Harry and Prince Seeiso of Lesotho, and has improved the lives of thousands of children by providing healthcare and education to those most in need, including children orphaned by the country's HIV/Aids epidemic.

Among the guests was David Furnish, whose partner Sir Elton John has helped raise money for a new Sentebale children's centre through the Elton John Aids Foundation's White Tie and Tiara ball.

Mr Furnish said: "I congratulated him on being an uncle and he smiled proudly. I'm an uncle many times over and I love it."

Sir Elton is currently in the South of France, recovering from a bout of appendicitis before surgery to remove his appendix.

Mr Furnish said of Sentebale: "At our ball we gave people the chance to purchase cabins at the new Mamohato Children's Centre, and we sold 10 cabins at £35,000 each. It was a huge success because people can see how it makes a difference to children's lives."

Other guests included the BBC newsreader Kate Silverton, who has seen the poverty of Lesotho first hand when she filmed a report there.

The Prince, wearing a blue suit and a white open-necked shirt, told an audience of 140 invited guests that he would not make a long speech because it was "absolutely roasting" in the small gallery off Oxford Street.

He said of the charity's work: "In the absence of parents for the vast majority of Lesotho children we at Sentebale we hope are filling the gap as best we can.

"The stigma that surrounds HIV and Aids must be explained and, I hope, understood."