Chris Evans is returning to British radio after more than three years.
The multi-millionaire will be heard on more than 200 commercial stations, including Virgin Radio, which famously sacked him in 2001.
They will be suspending their individual schedules with a single broadcast on Monday to raise money for children affected by the tsunami.
For Evans, whose high profile radio career began on the Radio 1 Breakfast show, it will be his first radio broadcast in three and a half years.
The millionaire, who recently split with young wife Billie, will be teaming up with presenter Kate Thornton for his slot in the 12-hour broadcast and interviewing British Prime Minister Tony Blair.
The likes of Capital Radio, Classic Gold and Virgin will come together for UK Radio Aid.
Others presenters include Big Brother hosts Davina McCall and Dermot O’Leary, and Johnny Vaughan.
Evans pulled in an extra one million listeners on his Radio 1 show. But he clashed with bosses, receiving warnings about on-air outbursts and “adult” content, and quit saying he had been forced out.
In 1997 he moved to rival Virgin Radio, bought and sold the company, and was then sacked in June 2001 following a drinking binge.
Today he said he was relaxed about being heard on Virgin again: “It’s fine. By Monday morning all hatchets will be buried,” he said.
Evans, 38, who has also been signed up to present the Brits next month, added: “It’s a very exciting thing to do.
“I haven’t donated in a major way yet, just put a few tenners in pub buckets. I’m just looking forward to it. I’m excited. I’m more nervous about the Brits.”
The broadcast will go out to an estimated audience of 20 million listeners and will be aired live from Capital Radio headquarters in London’s Leicester Square.
Each station will donate one day’s profits and listeners will be asked to donate one hour of their time or money to the appeal.