Tom Walker has joked he owes the Duchess of Cambridge royalties after their surprise duet saw his music go rocketing up the charts.

Tom Walker was accompanied by the Duchess of Cambridge on piano

Tom Walker was accompanied by the Duchess of Cambridge on piano

The 30-year-old singer was accompanied on piano by Catherine when he performed his track 'For Those Who Can't Be Here' for 'Royal Carols: Together At Christmas' and after the special programme aired on ITV on Christmas Eve (24.12.21), the song has enjoyed a surge in popularity.

He told The Sun newspaper's Bizarre column: “It was so well received, I probably owe her royalties now. She sent me a letter thanking me for the opportunity but it should be me thanking her.

“The song has jumped 57 places in the charts. It was a wonderful experience and she was so warm. She made the effort to thank all the musicians but it was us who felt so grateful to be part of something so special."

Tom, who met the duchess at a charity event for 'Action on Addiction', where he performed his single 'Leave A Light On', praised the 39-year-old royal for a "brilliant" performance but suggested she was nervous before recording the segment.

He added: “We met for a rehearsal beforehand and I gave her a recording of the track without the piano part so she could practise. It was obvious she had taken the time to perfect it. She was brilliant.

“You think the Royal Family almost don’t get nervous, they’re so used to the spotlight. But this was obviously a very different, new experience for her.”

Tom had admitted performing with the duchess had been a "crazy moment".

He said in an Instagram video to fans: "It was such an honour to be part of that, one of those pinch yourself, crazy moments.

"Playing your song with a member of the royal family is definitely not your everyday occurrence so I just wanted to say a huge thank you to the Duchess of Cambridge and the whole royal family for having me be a small part of an amazing service."