Antony and the Johnsons have won this year's Mercury Music Prize for the album I Am A Bird Now.
Chichester-born Antony Hegarty is now based in New York
Led by New York-based singer Antony Hegarty, they beat acts including Coldplay, favourites Kaiser Chiefs and hip-hop artist MIA.
The £20,000 award is for the best album of the year by a British or Irish act.
"I think they must have made a mistake," Chichester-born Hegarty said. "I am completely overwhelmed. I think that's insane."
The pianist and singer's winning album, features contributions from Boy George and Lou Reed.
Standing 6ft 4in tall and with a shock of black hair, the 34-year-old has a voice as unconventional as his looks.
The Mercury Music Prize was voted for by a panel of industry experts, journalists and artists, and is said to reward originality and creativity rather than sales success.
As he collected his award from host Jools Holland to a standing ovation, Hegarty said the competition was "a bit nutty".
"It's kind of like a crazy contest between an orange and a spaceship and a potted plant and a spoon - which one do you like better?" he said.
"What's really exciting about this night is just this wonderful biennial that shows the rich diversity of the spectrum of music that's going on at the moment.
Leeds band Kaiser Chiefs had been favourites to win
"It's been so wonderful to be here and just to meet everyone. I just love so many of the artists performing tonight, I think it's a bit bonkers to just give it to one person."
He performed at the Mercury award ceremony in London's Grosvenor House Hotel, as did fellow nominees Kaiser Chiefs, KT Tunstall, Seth Lakeman, Bloc Party, Polar Bear, Maximo Park, The Magic Numbers and the Go! Team.
Multi-million selling band Coldplay, nominated for their third album X&Y, could not attend the ceremony as they were on tour in the US.
Previous winners of the Mercury prize include hip-hop artist Dizzee Rascal, Primal Scream, PJ Harvey and last year's victors Franz Ferdinand.
Simon Frith, chairman of the judges, said Antony and the Johnsons won because they produced "such an extraordinary album".
KT Tunstall was among the other performers at the ceremony
"It's not like any album I've heard before or since," he said.
"It doesn't seem to have any obvious place where it's coming from - and yet play it to anybody and they're arrested.
"Some of them hate it, some of them absolutely love it - but nobody can ignore it."
The Mercury Prize was not designed to pick the least offensive album, he said, but to pick "a record that's really interesting, and this one is".
Chris Salmon, music editor of Time Out magazine, said it was a surprise choice.
"There were a lot of strong albums on there and I don't think a lot of people thought Antony and the Johnsons would be the one," he said.
"Some people thought of it as an American album - its whole genesis was in New York," he said.
"But he's got a beautiful voice and he writes beautiful songs, so in that sense it shouldn't be a surprise - but I think it still is."
Not to Hegarty's celebrity friends, however, who have been vocal in their support of the burly performer one critic described as having "a rugby player's build but the face of a medieval saint".
Lou Reed appears on Hegarty's award-winning album
"When I first heard him I knew I was in the presence of an angel," said Lou Reed.
"His amazing band contributes to one extraordinary experience of musical wit, depth and, most of all, beauteous heart."
Laurie Anderson has echoed her partner's comments, calling Anthony and the Johnsons "my favourite band in the whole world right now".
"Listening to Anthony's voice is like hearing Elvis for the first time," she said.
"When he sings it is the most exquisite thing that you will hear in your life."
"I Am A Bird Now is my favourite album this year," Portishead singer Beth Gibbons has told the BBC News website.
"I felt its honesty immediately and had not been that touched by music in a long time.
"He has expressed how I feel about being a woman better than I have myself and created an unnerving, unworldly yet direct impression of our fear of death and life's solitude."
Mercury Music Prize 2005 nominees:
Antony and the Johnsons - I Am A Bird Now Bloc Party - Silent Alarm Coldplay - X&Y The Go! Team - Thunder, Lightning, Strike Hard-Fi - Stars of CCTV Kaiser Chiefs - Employment KT Tunstall - Eye to the Telescope The Magic Numbers - The Magic Numbers Maximo Park - A Certain Trigger MIA - Arular Polar Bear - Held on the Tips of Fingers Seth Lakeman - Kitty Jay Did