As well as celebrities, cancer survivors and others who have been affected by the disease were invited to the bash, which was raising money for the Royal Marsden Hospital.
The Queen gave Prince William special permission to use the castle's State Rooms for the evening, though guests hoping to bump into Kate Middleton were left disappointed, as the Duchess of Cambridge was at home looking after Prince George.
As he met Ralph Lauren, William joked: “I'm sorry my wife's not here, you probably would far rather you saw my wife.”
He later delivered a speech to his famous guests, all of whom are friends or supporters of the hospital, saying: “I am enormously grateful to Ralph Lauren for his generosity, and to all of you who so kindly support the hospital. You should know that what you do saves lives and gives hope to thousands of people.”
Open Image Modal
Kate Moss laughs with Prince William
As well as the fashion designer, the Prince was photographed mingling with a number of his famous guests, and was even seen getting a laugh out of Kate Moss - an achievement if ever there was one.
He was also spotted speaking to 'Sherlock' star Benedict and the two looking like old friends as they chatted away at the fundraiser.
Open Image Modal
Prince William and Benedict Cumberbatch
Check out the gallery below for all the pictures from the star-studded fundraiser...
Prince William's Charity Dinner
Prince William Hosts Cancer Benefit(01 of19)
Open Image Modal
Kate Moss arrives at Windsor Castle. (credit:PA)
Prince William Hosts Cancer Benefit(02 of19)
Open Image Modal
Kate Moss and Jamie Hince pose on their way into the event (credit:PA)
Prince William Hosts Cancer Benefit(03 of19)
Open Image Modal
Cara Delevingne smiles for photographers outside Windsor Castle (credit:PA)
Prince William Hosts Cancer Benefit(04 of19)
Open Image Modal
Benedict Cumberbatch arrives for a dinner to celebrate the work of The Royal Marsden hosted by the Duke of Cambridge at Windsor Castle (credit:PA)
Prince William Hosts Cancer Benefit(05 of19)
Open Image Modal
Helena Bonham-Carter in her formal gown for the charity event (credit:Getty Images)
Prince William Hosts Cancer Benefit(06 of19)
Open Image Modal
Cate Blanchett arrives for a dinner to celebrate the work of The Royal Marsden hosted by the Duke of Cambridge at Windsor Castle. (credit:PA)
Prince William Hosts Cancer Benefit(07 of19)
Open Image Modal
'Wolf Of Wall Street' star Margot Robbie poses for photographers (credit:PA)
Prince William Hosts Cancer Benefit(08 of19)
Open Image Modal
The Duke of Cambridge delivers his speech to guests (credit:PA)
Prince William Hosts Cancer Benefit(09 of19)
Open Image Modal
Guests sit down for dinner at the benefit (credit:PA)
Duke hosts cancer hospital benefit(10 of19)
Open Image Modal
The Duke of Cambridge speaks with Emeli Sande at a dinner to celebrate the work of The Royal Marsden at Windsor Castle, Berkshire. (credit:PA)
Prince William Hosts Cancer Benefit(11 of19)
Open Image Modal
Prince William greets Kate Moss (credit:Getty Images)
Prince William Hosts Cancer Benefit(12 of19)
Open Image Modal
'Sherlock' star Benedict Cumberbatch meets Prince William (credit:Getty Images)
Prince William Hosts Cancer Benefit(13 of19)
Open Image Modal
Cara Delevingne and Kate Moss pose together at the event (credit:PA)
Prince William Hosts Cancer Benefit(14 of19)
Open Image Modal
Lily James, Cate Blanchett and Kate Moss at the event together (credit:PA)
Prince William Hosts Cancer Benefit(15 of19)
Open Image Modal
Prince William talks to 'Harry Potter' actress Emma Watson (credit:Getty Images)
Prince William Hosts Cancer Benefit(16 of19)
Open Image Modal
The Duke of Cambridge and Ralph Lauren (credit:Getty Images)
Prince William Hosts Cancer Benefit(17 of19)
Open Image Modal
The Duke of Cambridge manages to get a laugh out of Kate Moss (credit:PA)
Prince William Hosts Cancer Benefit(18 of19)
Open Image Modal
Cate Blanchett meets with Prince William (credit:PA)
Prince William Hosts Cancer Benefit(19 of19)
Open Image Modal
Cara Delevingne had changed into some more comfortable shoes by the end of the night (credit:Splash News)
href="http://www.facebook.com/HuffPostUKEnt"target="_hplink">LIKE US ON FACEBOOK