The Beatles legend Sir Paul McCartney celebrates John Lennon's 85th birthday

Today marks what would have been John Lennon's 85th birthday and Beatles fans have been celebrating around the world.

Joining them, Sir Paul McCartney posted a snap of himself with Lennon in what appears to be the 1969 Let It Be sessions, in the basement of Apple Corps on Savile Road, London.

Macca, 83, captioned his Instagram post: "Sweet memories on this day of a very special friend. Happy birthday John - Paul."

Lennon shares his 85th birthday with his younger son Sean Ono Lennon, who turns 50 today.

Widow and mother Yoko Ono, 92, shared a photo of her boys blowing out candles on a birthday cake together, captioning it: "HAPPY BIRTHDAY JOHN! HAPPY BIRTHDAY SEAN!" Meanwhile, the late Beatle' eldest son Julian, Sean's half-brother, also sent his best wishes.

Julian, the son of John and Cynthia Lennon, captioned his post: "Happy Birthday... Only Love.... Always...." The 62-year-old added to his brother Sean: "P.S. 50 is just a number..."