Neil Aspinall, who ran the Apple Corps music empire for the Beatles, has died at a hospital in New York, aged 66.
Beatles' pal Neil Aspinall died in New York aged 66
A school friend of Sir Paul McCartney and George Harrison, he was regarded by some of the band as the "fifth Beatle".
In an Apple Corps statement, Sir Paul, Ringo Starr, and the widows of Harrison and John Lennon paid tribute to "Neil's trusting stewardship and guidance".
Notoriously media-shy, Aspinall nonetheless fought hard to protect the Beatles' music, image and copyright.
Aspinall also played background instruments on tracks including Magical Mystery Tour, Within You Without You and Being for the Benefit of Mr Kite.
But it was for his stewardship at Apple Corps that he will be best remembered.
He was chief executive from 1970 until last year.
Throughout his career, he remained fiercely loyal to the group, looking after their business interests and taking legal action on their behalf.
He led the legal battle with Apple computers over the use of the Apple name and a royalties dispute between the Beatles and record label EMI.
He is credited with ensuring they continued to make money decades after they split up.
He was behind successful retrospective albums such as Beatles Anthology and Beatles One.
Apple Corps estimates that in his last 20 years at the company, the Beatles sold 70 million albums.
Neil Aspinall, top right, with the Fab Four, in 1964
Aspinall first befriended Sir Paul and Harrison at the Liverpool Institute Grammar School in the 1950s.
In The Beatles Anthology DVD, he described his first encounter with Harrison behind the school's air-raid shelters.
"This great mass of shaggy hair loomed up and an out-of-breath voice requested a quick drag of my Woodbine," Aspinall said.
"It was one of the first cigarettes either of us had smoked. We spluttered our way through it bravely but gleefully."
In 1961, he became the Beatles' road manager and drove them between gigs in his van before becoming their personal assistant.
Sir Paul, Starr and the widows of Lennon and Harrison said: "All his friends and loved ones will greatly miss him but will always retain the fondest memories of a great man."
In a separate statement, Starr added: "I've known Neil many years and he was a good friend. We were blessed to have him in our lives and he will be missed."
And Harrison's widow Olivia and the couple's son Dhani said: "Neil takes with him the love and history of his extended family.
"He was our constant and avuncular caretaker for so many years; there is no way to measure how much he will be missed."
Aspinall died at the Memorial Sloan-Kettering Cancer Center in New York City.
It's understood he was suffering from lung cancer.
He is survived by his wife, Suzy, and five children.