Sir Paul McCartney stages impromptu Covent Garden gig from the back of a truck

Former Beatle surprises a school choir and donates £20 to charity

Central London returned to the Swinging Sixties today as Sir Paul McCartney performed an impromptu gig from the back of a truck in Covent Garden.

Echoing The Beatles' final live performance from the roof of their record label's offices on Savile Row, there was a distinct touch of McCartney-mania in the air, despite the fact the gig at St Paul's Church had only been announced on Twitter an hour before.

As bemused tourists slowed to a halt amongst office workers glancing at their watches to see when lunch was up, people spilled out onto fire escapes and craned out of surrounding windows.

Performing a 20-minute set of songs from his latest album, titled New, Sir Paul got a warm reception from the crowd, old and young.

Despite retorting that she was "far too young" to have seen him live before, Louise Borjes, a 23-year-old student, still had no doubts. "It's Paul McCartney: of course he's going to be good!" she said.

For the Highclare School Choir, who had travelled from Sutton Coldfield near Birmingham to sing at St Paul's Church, the ex-Beatle provided an unexpected warm-up act.

As the choir sang a few bars of "Hey Jude" excitedly in the background, English teacher Kathryn Dawson had just one question: "How did we get Paul to support for us? He was actually supporting our school concert!"

Coming off stage at 2pm, just before Highclare School Choir trod the boards indoors, Sir Paul popped into the church, chatting with the students, posing for photographs and making a donation to the charity they were fundraising for.

"We're collecting for leukaemia, for our school charity, and he gave us £20," said Dawson. "He came right at the beginning, pulled a couple of students over and asked what we were doing. They gave him a leaflet and he gave us the money."

Paul McCartney with Highclare School Choir: Georgia Batchelor, Chloe Andrews, Louise Chung, Billie O'Shea and their teacher Jennie Thornton (Oscar Quine)

Sir Paul was in high spirits for his performance, joking with the crowd: "This is a change from the 60s because we would just have been coming in from the clubs right now."

He was watched by his daughter, fashion designer Stella, and her two children from a facing balcony.

Inside, the choir performed contemporary classics such as "California Dreamin" and "Say a Little Prayer", but The Beatles didn't quite make the cut.

"I think they're really good," said 14-year-old choir member Georgia Bachelor. "Although I've never really heard much of their music."