The note, which begins “Dear Princely person”, reveals MCCartney asking for a donation to help establish the Liverpool Institute for Performing Arts, which the former Beatle co-founded in 1996.

According to Boston’s RR Auction company, the letter sold this week (ends17Jul16) for a price of $14,822 (£11,233). The undated letter is signed "Paul McCartney" at the top of the first page, above his London address, and features "Paul (MCCartney)" at the sign-off. “Hope you didn't mind me writing this, it's so long since I've written letters I feel like I'm back at school myself,” the note reads. “Who knows, it may turn out to be something special for thousands of future kids. Thanks for looking at this.” One humorous section of the note finds MCCartney asking Prince to attend a future class and "teach (them) some moves!!" MCCartney also sketches a smiley face at the end.

RR Auction’s Robert Livingston says that it remains unclear whether Prince made a donation to the school. “The vast majority of his contributions were gifted anonymously,” he said, adding that the document was rather unique. “It is an incredible letter with personal content relating to MCCartney’s philanthropic efforts to extend the gift of music to future generations.”

After Prince’s death from a fentanyl overdose at the age of 57 in April (16), music legends across all genres expressed their sympathies. MCCartney, 74, recalled spending New Year’s with the musician, writing, "he seemed fine and played brilliant funk music."

And in May (16), MCCartney played a concert in Prince's hometown, Minneapolis, and consoled the crowd with a cover of the icon’s hit Let’s Go Crazy.

Among other items to be sold at the auction was a Beatles and Jimmie Nicol signed Danish programme for a Beatles performance on June 4, 1964. It sold for $11,000 (£8,336).