Sir Paul McCartney is in mourning after his brother-in-law John Eastman died aged 83

John was the brother of Paul's first wife, Linda Eastman McCartney, killed by breast cancer aged 56 in April 1998.

He also helped The Beatles' frontman navigate the band's breakup and his solo career after that, among other projects within his music career.

Paul shared the news of his death with a long message alongside a picture of the pair of them doing a yoga pose together.

He said: "My dear brother-in-law, John Eastman, has passed away. Having known each other for over 50 years it is an extremely sad time for me, and our families.

"John was a great man. One of the nicest and smartest people I have had the good luck to have known in my life."

Paul continued his message: "Not only did he help me massively in my business dealings as my lawyer but as a friend he was hard to beat. His sense of humour always shone through in everything he did and his devotion to his family was supreme.

"We had so many fun times together through the years, but when the time came to be serious, he was unbeatable. There is so much more that can be said of his incredible qualities, but words can hardly describe his passion for life and our affection for this amazing man.

"He will be sorely missed but always held dear in the hearts of those of us who knew and loved him. See ya Johnny! Love Paul."

John last year made headlines for purchasing a luxury $26.5 million (£22

million) penthouse overlooking Central Park in New York City.

The entertainment lawyer was also involved in a family dispute over the estate of his father, Lee Eastman, which was valued at more than $300 million (£246 million) as reported by the New York Times in 2007.

John is survived by his wife, Jodie Eastman.