William says he sees charity as 'catalyst for change'
Prince William has said he and his new wife want to use philanthropy as a "catalyst for meaningful change".
He was speaking at a star-studded charity dinner - the Duke and Duchess of Cambridge's first official engagement since their wedding.
The duchess wore a shimmering nude gown by Jenny Packham at the Ark Gala in fields behind Kensington Palace.
The duke announced a joint venture by the Foundation of Prince William and Prince Harry and the Ark charity.
The £10,000-a-head gala dinner marked the 10th anniversary of Ark - Absolute Return for Kids - which was set up by financier Arpad Busson and sponsors academy schools in the UK and programmes for disadvantaged children around the world.
In a speech, the duke said he had enjoyed many advantages growing up, and he and his brother wanted to use their position to help.
"So many young people do not have these advantages and as a result can lack the confidence and knowledge to realise their full potential," he said.
The prince explained that the joint venture would be a four-year programme and create opportunities for children in UK, then later expand to projects in sub-Saharan Africa.
At a canape reception before dinner, the duke and duchess mingled with some of the more prominent figures or chatted to associates of Mr Busson.
Mr Busson has two sons - Flynn, 13, and eight-year-old Cy - with his former partner, model Elle Macpherson, and the royal couple chatted and joked with the two boys.
They were the centre of attention with people crowding around them to get a view of the newlyweds or take their picture on camera phones.
After about 45 minutes, they made their way into an enormous marquee which was filled with almost 100 tables.
Among the guests seated on the duke and duchess's table were Oscar-winning actor Colin Firth, actress Liz Hurley, socialite Jemima Khan and broadcaster Mariella Frostrup.
Elizabeth Murdoch, the daughter of media tycoon Rupert Murdoch, also had a place as did Anish Kapoor, the British-based, Indian-born sculptor who won the Turner Prize in 1991.
The duchess sat between Crown Prince Pavlos of Greece, a distant relative of William, and Mr Busson, while her husband was opposite her with socialite Countess Debonaire von Bismarck on his left and Princess Marie of Greece on his other side.
A charity auction held by auctioneers from Christies offered lots including a Kenyan safari for 10 people, a luxury tree house and a sailing regatta on the world's biggest sailing yacht, the Maltese Falcon.
Artist Tracey Emin also donated one of her works for the auction.
Each place setting at the black-tie dinner had a small touch-pad computer for the diners to make pledges and bids.
Bidding for the items reached six figures and organisers were hopeful they could beat last year's total of £14m.
The entertainment included a high dive show and musician Mark Ronson, and a mystery band - rumoured to be the Kings of Leon - were expected to perform.