Saundra Glenn, 64, who has osteoarthritis and problems in her hip, knee and ankle, nearly went home after she was struggling to walk to the accessibility box office at the entrance of the festival.
It came after a campaign by Luton Town fans for the group to change the lyrics of its song Yellow to Orange due to the club's colours being orange and the team's rivalry with Watford.
The Espresso hitmaker, 25, pulled out all the stops in a plunging orange mini dress as she performed alongside the likes of Coldplay and Olly Alexander at Stockwood Park in Luton on Sunday.
Just after working her way through songs like Ice Cream Man, Secrets and her signature track Escapism, she admitted to the crowd that she had some self-doubt.