When a gang of mates in Leeds decided to form a band three years ago, they had the limited aim, they claim, of blagging a spot at their home town's festival.

They did ­ and more. Last night, Kaiser Chiefs stormed the most prestigious awards in British rock and pop, the Brits, to take three top honours. They brought a dash of riotous assembly to a ceremony whose other big winners were those epitomes of middle-class good taste, James Blunt and Coldplay.

The band were named best British group, best British rock act and best British live act of the year, beating rivals including Franz Ferdinand, Hard-Fi and Gorillaz at the music industry event at Earl's Court, London.

They acquired a fan on stage when a stranger breached security to join them as they took their first award. The band looked bemused as the man waved an apparent award of his own, with the normally voluble frontman Ricky Wilson silenced by the gatecrasher's appearance.

Yet he had regained his composure by the time the Chiefs, who were virtually unknown a year ago, returned for their third gong. "We've been thinking of stuff to say that's funny all day and we've come up with nothing," Wilson said.

However, they were scuppered in the prestigious MasterCard British album honours by the juggernaut of Coldplay's international bestseller, X&Y. And "Speed of Sound", the single taken from X&Y, also fought off stiff competition to take the British single prize.

Yet Chris Martin also appeared to be announcing the band's retirement from the public arena, saying: "You won't see us at one of these for many, many years."

James Blunt took best British male soloist. "I've been accused so many times of singing like a girl. Now I've won best British male artist, maybe it will remind me to sing more like a man in future," he said. He also became the first product of Harrow, Sandhurst and the Household Cavalry to take the British and international pop act prize.

Arctic Monkeys, whose internet word-of-mouth success netted them the highest first-week sales recorded for a debut album, were honoured with the British breakthrough-act prize.

K T Tunstall, the Scottish singer-songwriter whose last-minute appearance on Jools Holland's late-night TV show transformed her career, won the best British female solo artist category but offered a part of it to Kate Bush. She concluded one of the more coherent speeches with a rallying cry: " Ladies, disregard your limits."

Paul Weller, formerly of The Jam and The Style Council, was honoured with an award for his outstanding contribution to music. It was presented by the actor Ray Winstone who said the musician was "someone I consider a genius".

Closing proceedings with a set which brought hundreds of people to their feet, Weller said: " It's been a great 30 years and there's a few more years left hopefully."

Last night's ceremony included performances from many of the winners including storming sets from Kanye West, who was supported by 77 scantily clad women in a display akin to a Miss World pageant, Gorillaz, with their choir of 100 children, and Prince in his first appearance at the ceremony since 1997.

Madonna was also cheered loudly when she was named best international female artist, but fuelled the speculation of marriage difficulties when she apparently ignored efforts by husband Guy Ritchie to kiss her as her success was announced.

The winners

British male solo artist - James Blunt

British female solo artist - KT Tunstall

British group - Kaiser Chiefs

MasterCard British album - Coldplay X+Y

British rock act - Kaiser Chiefs

British urban act - Lemar

British breakthrough act - Arctic Monkeys

British live act - Kaiser Chiefs

British single - Coldplay 'Speed of Sound'

British and international pop act - James Blunt

International male solo artist - Kanye West

International female solo artist - Madonna

International group - Green Day

International album - Green Day American Idiot

International breakthrough act - Jack Johnson

Outstanding contribution to music - Paul Weller