British-Sri Lankan rapper MIA walked out of the ceremony within minutes of the announcement that Antony and the Johnsons had won the £20,000 Mercury Prize.
Yet the 6ft 4in singer-songwriter, who was born in Chichester and these days lives in New York, proved a popular choice among most of the bands, critics and record label executives attending the prestigious awards ceremony at the Grosvenor Hotel in London.
Accepting the prize from the presenter Jools Holland, Hegarty, 34, suggested it must be a mistake. "I'm completely overwhelmed. I think that's insane," he said.
Commenting on the nature of the music prize, which is open to all kinds of contemporary music from pop and rock to jazz and folk, he added: "It's kind of a crazy contest. There's like an orange and a spaceship and a potted plant and a spoon. Which one do you like better? It's mad."
Hegarty, who silenced the room when he performed with his band of a cellist and a violinist last night, won the prize for his album I Am a Bird Now, which was released in March this year and which included contributions from Lou Reed, who has acted as a mentor to him, as well as Rufus Wainwright and Boy George.
With a haunting, ethereal voice suggestive of the choirboy he once was, the Mercury judging panel had said: "Pianist and torch singer Antony has a voice to pin you to the wall - and songs that send shivers down the spine."
The Kaiser Chiefs had been the bookies' favourite and although they made no comment last night, drummer Nick Hodgson last month said of Hegarty: "He's an American really. It's a good album, but it's daft he's got in on a technicality."
Apparently conscious of the row, Hegarty cited British musical influences from Boy George to Marc Almond as being a formative part of his education but avoided a direct answer to the question as to whether he still felt British.
"My thing is really mixed up because I've been moving around my whole life," he said. "I take my inspiration from really soulful singers and there are a lot those in England, Great Britain."
The prize, which was won last year by the Glasgow art rockers Franz Ferdinand, had seemed to many an open contest this year with acts from the tuneful harmonists Magic Numbers to the Sri Lanka-born singer MIA, who mixes hip-hop, ragga and pop, all with their supporters.
Holland said he had been asked by the judges, who included the broadcaster Lauren Laverne and Ian Parkinson, managing editor of Radio 1, to stress how tough a decision it had been because "all of the albums have been so wonderful".
The other shortlisted albums were The Magic Numbers by the Magic Numbers, Arular by MIA, Held on the Tips of Fingers by Polar Bear, Employment by Kaiser Chiefs, A Certain Trigger by Maximo Park, Stars of CCTV by Hard-Fi, Eye to the Telescope by KT Tunstall, Silent Alarm by Bloc Party, Kitty Jay by Seth Lakeman, X&Y by Coldplay, and Thunder, Lightning, Strike by the Go!Team.
Kaiser Chiefs opened the ceremony with a blistering performance. Seth Lakeman, a folk violinist and singer from Dartmoor, used his appearance on the prize stage to say thanks for the blast of publicity for folk music, while MIA - Maya Arulpragasam - originally a refugee from Sri Lanka, praised Britain for making it possible for someone like her to be at the ceremony.
"England is my home and I feel this couldn't have happened to me anywhere else in the world, even in Sri Lanka or America. Britain is the only kind of country that can let somebody come over and go through the motions and get experience of every class, every creed, every nook and cranny.
"I think it's really great that in the climate of what's going on to be someone up here saying thanks. Hopefully this is the positive side of England."
* 2004: Franz Ferdinand
* 2003: Dizzee Rascal
* 2002: Ms Dynamite
* 2001: PJ Harvey
* 2000: Badly Drawn Boy
* 1999: Talvin Singh
* 1998: Gomez
* 1997: Roni Size/Reprazent
* 1996: Pulp
* 1995: Portishead
* 1994: M People
* 1993: Suede
* 1992: Primal Scream