The biggest night of 12-year-old Shaheen Jafargholi’s life was meant to come next Monday — he was due to sing a duet with Michael Jackson at the singer’s comeback London concerts at the O2 arena.

Instead, the Britain’s Got Talent finalist found himself on stage as the sole British performer alongside the grandees of showbusiness at Jackson’s memorial service.

An expected television audience of a billion people had expected to see Stevie Wonder, Mariah Carey and Smokey Robinson at the Staples Centre in Los Angeles. But few had predicted the presence of Shaheen, who lives in Swansea with his mother, Karen, 39, and their cat, Muffin.

Shaheen, who sang the Jackson 5 hit Who’s Lovin’ You, which he had performed on the ITV show, got a standing ovation from the audience as he successfully negotiated the first step on his way to global stardom. Although he does not yet have a recording contract he is tied to Simon Cowell’s Syco, a division of Sony, as part of a three-month deal that all finalists on Britain’s Got Talent sign.

A source close to Cowell said that no decisions had been taken on Shaheen’s future but the music mogul was keen to secure his services. “With a billion people watching, it’s safe to say that he’ll be pretty hot property,” the source said.

Shaheen told The Times that he was approached by representatives of Jackson’s family on Friday. “I couldn’t believe it,” he said. “Michael Jackson has always been my hero and apparently he had seen my audition tape for the Thriller Live tour in which I played the younger Michael Jackson. It had really impressed him.

“It’s an absolute dream come true. I can’t believe I am among my idols, such as Mariah Carey and Lionel Richie. It’s been amazing hearing my name being shouted, and to be flying the flag for Swansea. It’s out of this world and will only sink in when I get home.”

Shaheen has just finished performing on the Britain’s Got Talent live tour, and had previously appeared as a young Michael Jackson in a touring production of Thriller Live. He told The Times: “Michael Jackson’s death was a complete shock. It devastated me, so performing at the service is a silver lining.”

He said that it had been really hard to sing Who’s Lovin’ You while on the TV show tour. “It was very emotional. Coming to LA to sing at the memorial service, I was a little bit nervous but who wouldn’t be? I took it all in my stride.

“I haven’t really thought about success in America — the whole thing has been such a whirlwind I haven’t had time to think about the future. I’m just enjoying what I do day to day and can’t believe I am on stage with these amazing icons.

“In the future I would love a career in singing and to be as successful as my idol, Michael Jackson.”

Robert Phillips, 53, the headmaster of the Dylan Thomas Community School in Swansea, gave special permission for Shaheen to be absent this week.

Mr Phillips said: “We are very proud. Shaheen was asked specifically by Michael Jackson’s closest family to sing at the service because they knew how impressed Michael had been with him.

“I got a call from Shaheen’s agent asking for him to be released from school and then we were told why.”

Explore Music

• CD Reviews

• Live Reviews

• Classical

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010