Biffy Clyro say Nick Knowles was "very nice" when they met but they denied a jamming session ever took place.
The Scottish rockers have opened up on the chance meeting after the ‘DIY SOS’ star suggested an impromptu evening with the band led to his first record deal and a move towards music.
However, drummer James Johnston told BBC Radio 1’s Greg James: "He was a nice guy! I’m not gonna say anything bad about him, Mr Nick Knowles, he was lovely.
"But I don’t think it’s quite the ‘Kum Ba Yah’ situation that everyone might have in their heads. I’m really sorry to shatter the illusion that we had a proper heavy jam with Nick Knowles, because that did not happen I’m afraid.
"It’s a half truth. We were in the same rooftop bar at the same time, and he was very nice."
Nick – who is currently starring on reality show ‘I’m A Celebrity… Get Me Out Of Here!’ and released debut album ‘Every Kind Of People’ last year – told his fellow campmates that he was offered his deal with Universal after bosses heard him playing songs with the ‘Many of Horror’ stars.
He claimed: "My brother’s a really good musician and I’ve always played along with him and a couple of years ago somebody heard me, I was playing on a rooftop bar in Soho with some other bands…
"Somebody from a record company saw me doing it and I got a phone call saying, ‘I’m from Universal, want to do an album?’ "
However, James – who is in the group with Simon Neil and brother Ben Johnston – has played down this version of events and admitted he remembers it quite differently.
He added: "He’s been a bit fast and loose with the truth there. It was more like eight years ago, and it was after an awards ceremony.
"We came back to this hotel in Soho and we’d been informed that Nick Knowles had bought us a bottle of champagne to celebrate on the roof! He was lovely, we had a drink and we left and there might have been a guitar there."
Biffy Clyro: Nick Knowles has been ‘fast and loose’ with the truth
