Simon Cowell memorably had to eat his words when he first heard the duo Jonathan and Charlotte sing on Britain’s Got Talent back in 2012.

Jonathan Antoine and Charlotte Jaconelli’s performance of The Prayer brought the audience to their feet at their audition – and Cowell compared Jonathan’s voice to Pavarotti’s. He also advised Jonathan, then 17, to dump his 16-year-old co-singer because he thought she would hold him back in the competition, but Jonathan refused and in the semi-final Simon admitted it was the best decision Jonathan had ever made.

In the final, they came second, beaten only by dog trick act Ashleigh and Pudsey, and released two albums, selling a quarter of a million copies.

Jonathan and Charlotte split as a duo in 2014 and both singers have launched solo careers, with Charlotte, now 20, releasing her solo album Solitaire in 2014. “I’m very driven when I get my head set on something,” she said as the album was launched. “I’m very determined.”

After performing in concerts at the London Palladium and the Royal Albert Hall as well as making her concert debut at 54 Below in New York last September and supporting G4 on their UK concert tour, including their date in Worthing, she will be back in Worthing next month to sing a series of classical and musical numbers.

Musical theatre is one of her three great loves, alongside classical and contemporary pop, and is “entirely unashamed” of her love for the genre. “They’d never let me put my iPod on at house parties, let’s put it that way,” she laughs.

Charlotte and Jonathan both grew up in Essex and were paired as singers at their secondary school in Chigwell by their singing teacher. At a suggestion by head of music Ginette Tomlinson, they sang The Prayer for their GCSE – and at their teacher’s wedding - and Charlotte went on to train full-time in Musical Theatre at the Arts Educational Schools in London while Jonathan attended the Royal Academy of Music.

Charlotte recalls the moment she applied for Britain’s Got Talent: “I was sitting at my computer watching ITV Player and the audition advert popped up. I thought, ‘Why not?’

“When I put in for Britain’s Got Talent, I didn’t tell Jonathan. We even forgot to go to the first audition. Then they got in touch and said we had another chance, which I took as a sign.”

The two remain good friends, ended their act as a duo only because after recording two albums together they realised there wasn’t enough material that suited their voices together to make a third.

“We needed to break out and do our own thing,” she says. “But we certainly haven’t put anything in the way of coming back and doing something else together in the future.

“Jonathan, having studied at the Royal Academy, was obviously into classical music whereas the first classical I’d ever sung was on Britain’s Got Talent. I’ve studied musical theatre since I was four, so I was suggesting songs from classical musicals.

“When we first started singing, the duets were a bit of a novelty for us, something that we’d do at the end of a show at school or in a church hall.”

Charlotte will be singing songs from West End Musicals and classical music during an evening of music in Worthing this month when she performs with Classical Reflection, identical twins Naomi and Hannah Moxon appeared on BBC 1’s The Voice last year, and Karl Loxley, who appeared in the same series of The Voice when he sang Nessun Dorma and Your Song.

• Charlotte Jaconelli in Concert is at the Pavilion Theatre, Marine Parade, Worthing, at 7.45pm on Saturday April 2. Tickets: various prices. For details, phone 01903 206206 or visit worthingtheatres.co.uk.