Prince William has been patron of Centrepoint for several years
Celebrities will join hundreds of people sleeping rough on Thursday night to raise money for a homeless charity.
Centrepoint hoped the sleep-out in east London's Spitafield's market would help raise more than £250,000 to help house young homeless people over Christmas.
Casualty actor Joe McFadden, Loose Women presenter Lisa Maxwell and Radio 1 DJ Sara Cox will be among those sleeping rough for the night.
The charity's patron Prince William called the event "a superb initiative".
He said the event "demonstrates how incredibly tough it is to be homeless".
"The more people who understand the devastation inflicted on young lives by homelessness, the more Centrepoint can do to support those same young people," he added.
"Young men and women are driven to homelessness for all sorts of reasons, and the support that Centrepoint offers can be life-saving and life-changing."
More than 200 people are expected to give up their beds for the night in support of the charity, which cares for homeless people aged 16 to 25.
Centrepoint's chief executive, Seyi Obakin, said the charity''s "fantastic" supporters "face the discomfort of sleeping rough, but with one big difference - they have the luxury of returning home in the morning."
"We hope the sleep-out will not only raise awareness of youth homelessness but provide vital funds to give more homeless young people a safe place to sleep, where they can start to build a brighter future," he added.