The Duke of Cambridge will tonight make his first public speech as a married man at a lavish £10,000-a-head fundraising dinner.
The 900-guest black tie Ark Gala dinner at Kensington Palace is the first official public engagement for the Duke and Duchess since returning from their Seychelles honeymoon.
But the Royal couple's attendance at the annual event has drawn criticism from some quarters, after extensive efforts had been made to distance their April wedding from over-extravagance.
The Prince is expected to use the event to announce a collaboration between his and Prince Harry's 'Prince's Foundation' and Ark (Absolute Return for Kids), co-founded by 48-year-old Swiss financier Arpad Busson.
Mr Busson - whose event charges upwards of £50,000 for a table of ten - has an on-off relationship with actress Uma Thurman and has two children with former supermodel Elle Macpherson.
The Ark charity helps to raise money for projects helping some of the world's poorest children.
The glitzy dinner - which will feature DJ Mark Ronson and band Kings of Leon - will also hold an auction which could see the rich and famous part with millions of pounds.
The ostentatious marquee event takes place in Perks' Fields behind Kensington Palace, days after it was announced the Cambridges will move into the royal residence in the coming weeks.
Kensington Palace is also where the Prince spent years growing up with his mother Diana, Princess of Wales.
William and Kate's attendance at the fundraiser has been made possible because the Duke is not on duty at RAF Valley.
The couple are in London to coincide with Trooping the Colour, the Queen's official birthday celebration, which this year also falls at the same time as the Duke of Edinburgh's 90th birthday.
The invitation to the dinner - a perspex paperweight - explains 'carriages' will be at 2am.
A spokeswoman for Ark said: "Over the past ten years Ark's programmes in the UK, Southern Africa, eastern Europe and India have transformed the lived of more than 200,000 children."