Thousands of people were gifted a surprise U2 gig in the heart of their home city of Dublin, as the band marks 50 years since its formation.

Crowds packed into Grafton Street, one of Dublin’s main shopping thoroughfares, as the band played some of their greatest hits from a balcony on Bewley’s Cafe on Friday evening.

Earlier that morning, they returned to the Dublin school at which drummer Larry Mullen first sought out his fellow bandmates five decades ago.

The Irish rockers put on a special performance at Mount Temple Comprehensive School in front of hundreds of students on Friday.

This month in 1976, Mullen is said to have pinned a note stating “Drummer seeks musicians to form band” on the school noticeboard.

He joined Bono, whose real name is Paul Hewson; The Edge, whose real name is David Evans; and Adam Clayton for 30 minutes of music – in a recreation of when the international music stars used to play at the school’s boiler house.

They are among the world’s best-selling music artists, having sold 170 million records.

It comes as the band promote their new album Carnaval De Luz, which features a duet between Bono and Dolly Parton.

It is the band’s 16th album and the first of new material since Songs Of Surrender in 2017.

There was a carnival atmosphere as hundreds of children crowded into an area of open ground beside the school boiler house, while others stuck their heads out of the surrounding classroom windows.

News of the unique gig, which was attempted to be held as a closely guarded secret, had clearly broken out beyond the grounds as fans outside the gates – and builders several stories up on a nearby construction site – also sought to catch a glimpse of the excitement.

A major production with several moving cameras captured the performance, which was blasted over a loud sound system across the schoolyard into the surrounding Clontarf.

Taking to the stage after the system played Alice Cooper’s Schools Out, Bono grabbed the mic and pointed to the school science lab.

Before launching into I Will Follow, he joked to the school: “We escaped the lab – how’s the experiment going for you?”

The quips kept coming with some educational advice before the opening “uno, dos, tres, catorce” countdown for Vertigo, Bono said: “If you’re taking Spanish lessons, don’t take them from me.”

An Irish tricolour waved as the crowd heaved and jumped along – with Bono noting the students were “out of control”.

While at times short for words due to the spectacle, the Dubliner said Ireland was an island full of sound and music, adding: “We’re so proud to be Irish.”

Reflecting on their time at the school and paying tribute to their teachers, Bono said: “Learning how much you need to be taught was – and continues to be – the humblest and hardest lesson for the four of us.

“Part of that started here and the sense was that maybe all we needed was around us, just under our feet – if we could see it in our mates, our wider community that was going to help us get through the next 50 years.

“So we want to thank them – and the wider community around this rock ‘n’ roll high school.”

Children cheered “I love you Bono” as the multi-generational audience sang along and took videos and pictures.

On behalf of the band, he thanked them for turning up but noted the children of the “rock ‘n roll high school” had “nowhere else to go” during the afternoon gig.

Supported by children on traditional Irish instruments from the Music Generation, a national music education programme supported by the band, those gathered were also treated to a rendition of One.

A chanted demand of “one more tune” elicited an encore of With Or Without You before the band left the improvised stage of the boiler house – 50 years after coming together.

Thousands more gathered on Dublin’s Grafton Street later that day as the Bewley’s appearance became the city’s worst-kept secret.

Bono noted the band’s “birthday” as it paid tribute to recently deceased Irish musician Glen Hansard by playing his track Falling Slowly, while the Dubliners also sang along to a chorus of Molly Malone.

Earlier, entertainment reporters were given a sneak preview of the upcoming album including songs Silencio, Can’t Stop Us Now, and The Greatest Show on Earth at a listening party at the Twenty-Two venue – which had been given a full makeover with U2 memorabilia and rebranded back to its former title of McGonagles, where the band has played more gigs than anywhere else.

Among the selected tracks was Torn, which is a duet between Bono and the late country music star Dolly Parton.

Parton, who died in August at the age of 80 following a brief battle with cancer, sings from the perspective of the matriarch of a family which is being torn apart due to the differing political views of two sons.