The two-piece grunge band - made up of brothers Eoin and Rory Loveless - took to the stage at the O2 Academy Brixton in London and Eoin admitted he was worried about playing as The Beatles legend looked on.
Speaking before their performance, Eoin told BANG Showbiz: ''Well, everyone is a musician [in the audience] aren't they? Everyone's got their music taste we just have to do what we do and if Paul McCartney doesn't like it we'll just have to live with that. This is the highest concentration of musicians we've ever played in front of.''
The 'Bloodsports' singers were up for Best Live Band, but lost out to the Arctic Monkeys, and Eoin insists they couldn't have put bets on who would win, saying: ''I don't think you can even bet on our category.''
Although the duo weren't bothered about walking away from the ceremony with a prize, one of their competitive friends was desperate for them to be victorious.
Eoin said: ''We've got a competitive mate with us in the band and he's been just so annoying about the ward. Any chance to wind us up or get us agitated he went for it.''
Other performances on the night came from Blondie - who won the Godlike Genius Award - The Horrors and Metronomy, who opened the show along with MKS with 'Love Letters', which is from their forthcoming new album of the same name.
Take a look back at October's inaugural event.
The film is expected to continue without Mendes' involvement.