A young man who believed Prince William to be Prince the singer has written to the heir to the throne to apologise for his confusion.
Prince William recalled the hilarious mix-up during his appearance on The Graham Norton Show last Friday, sitting on the famous red sofa alongside Hollywood stars Cate Blanchett, Hannah Waddingham and Robert Irwin.
But he didn't name 22-year-old Sebastian Smith, who he met while on a visit to Sweet Surprise cafe in Ilminster, Somerset, on October 6.
The cafe offers training for adults with learning difficulties in the workplace - including Sebastian, who has the rare genetic disorder Rubinstein-Taybi Syndrome.
Prince William spoke of meeting a 'lovely gentleman', who looked at him and asked 'When are you going to sing?'
The 44-year-old royal added: 'It turned out he wanted me to sing Purple Rain, which I don't know the lyrics for.'
Prince William pictured chatting to Sebastian Smith (second from left) who thought the royal was pop singer Prince
The royal met Sebastian (pictured) at Sweet Surprise cafe in Somerset, which offers workplace training for adults with learning difficulties
Prince William said the mix-up was apparent when Sebastian asked him politely: 'What are you going to sing?'
Sebastian's family came forward after the royal told of the encounter on the popular BBC chat show, explaining that he is a massive fan of the pop singer - who died in 2016.
Sebastian's mother said of the sweet moment: 'To be honest, I don't think Sebastian had any idea who Prince William was - but he's a massive fan of Prince the singer and can list all his songs and knows all the lyrics.
'Considering his learning difficulties, it is amazing.
'So when Prince William arrived at Sweet Surprise, Sebastian assumed it was Prince the singer!'
She added that her son has now penned a letter to Prince William and hopes that the royal will read it.
The Prince of Wales recalled the hilarious encounter on the famous red sofa last Friday night, delighting the studio audience as he showed off his more relaxed side
He appeared on the hit BBC chat show alongside Hollywood stars Cate Blanchett, Hannah Waddingham, Robert Irwin and singer Jorja Smith
'We've helped Sebastian write a letter to Prince William. In it, he thanks William for visiting and has apologised for mistaking him for Prince.
'We hope he sees it,' she said, adding that he was loving all the attention.
Prince William's appearance on The Graham Norton Show last week was a royal first, as the future King delighted the studio audience by regaling them with personal stories and showed off his more relaxed side.
The future King, who was greeted by gasps when Norton announced his arrival, opened up about his unlikely childhood career ambitions, his love of football and the television programmes that have his children hooked.
The Prince of Wales revealed he once dreamed of becoming a police officer and secretly posts comments on Aston Villa fan forums, allowing him to share his passion for the Premier League club away from the spotlight.
The Prince also confessed that before accepting his royal destiny, he had considered a career in the police.
He later also developed ambitions of becoming a DJ, although his attempts to establish himself behind the decks were apparently less than successful.
'Then I went through a phase of wanting to be a DJ, which didn't go very well. I was called DJ Xara, with an X,' he revealed.
But his confession failed to impress Ted Lasso star Hannah Waddingham, who jokingly responded: 'Oh that's rubbish.'
William appeared entirely at ease with the teasing as he joined in the light-hearted conversation, in a rare glimpse of the man behind the royal title.
His appearance was intended to promote his Earthshot Prize, the environmental initiative he launched six years ago to support innovative solutions to some of the planet's biggest challenges.
But the conversation also offered an insight into life behind palace doors, including the Wales family's television habits.