London Mayor Sadiq Khan joked he was hoping he would be invited to join boy band The Vamps as he welcomed musicians to the city ahead of International Busking Day.
Mr Khan admitted he could not play the guitar as he posed with the instrument and three of the four members of the band on the steps of the National Gallery in Trafalgar Square.
He was also joined by rapper Tinchy Stryder and singer Jessie Ware as he insisted the vote to leave the European Union will not mean London will be closed to talent and creativity.
He said: "London is open. We have to send a message that we are open to business and talent and investment and trade.
"I was concerned the impression was given post-Brexit that London is closed off, but London is open.
"We have the best of London this weekend with street performers and buskers.
"Tomorrow's Ed Sheeran could be today's busker."
But Mr Khan admitted he will not be taking part in performances, saying: "My daughters have forbidden me from singing in public. I'm hoping The Vamps will sign me up."
If he were to sing, he said there could only be one choice of song: "London's Calling."
One Direction star Niall Horan, Pulp frontman Jarvis Cocker and actor Jude Law are among the other stars who have backed the mayor's #LondonIsOpen campaign.
International Busking Day, which takes place on Saturday, will be celebrated in 50 cities around the world and in more than 50 locations around the UK to celebrate street performance.
Members of The Vamps, who performed two songs in Trafalgar Square to a crowd of screaming girls, began as buskers before scoring hits with songs including Wake Up, Somebody To You and I Found A Girl.
Singer Brad Simpson told the Press Association: "We started from busking, we individually busked on the streets of our home towns before we started as a band, so it was fun to perform on the streets again.
"When you're busking you learn the best ways of doing something, it's trial and error, so when you find something that clicks you try to replicate it and do it better next time."
As for his secret to ensure he got the attention of busy commuters, he said: "Wonderwall always does well. Or turn up the amp really loud so they can't ignore you."