Sir George Martin, the record producer known as the "Fifth Beatle", has died aged 90, Ringo Starr has said on Twitter.
Sir George helped the Beatles achieve global success as the head of the Parlophone record label after hearing their demo tape in 1962.
Starr, 75, tweeted: "God bless George Martin peace and love to Judy and his family love Ringo and Barbara. George will be missed."
He captioned a picture of the Fab Four and Sir George with the phrase: "Thank you for all your love and kindness George peace and love."
Sir George studied at Guildhall School of Music and played the oboe professionally in London before joining the recording industry.
Over his career, he was awarded two Ivor Novello awards, six Grammys and in 2008 was the recipient of the Grammy Foundation's Leadership Award.
In 1965 he was nominated for an Academy Award for his work on the music in A Hard Day's Night and in 1984 he received the Brit award for outstanding contribution to music, having been named best British producer at the first Brit awards in 1977.
In 2012, the BBC filmed a documentary about his life, Produced By George Martin.
Up until his death, he continued to write music, work with charities and advise broadcasters, according to the website for the independent music publisher he set up in 1969.
His son Giles is also a producer who has worked at Abbey Road studios, where Sir George helped the Beatles perform the world's first live global broadcast.
Tributes for Sir George flooded in from within and outside the music industry.
Sean Ono Lennon, son of John and Yoko, posted a picture of Sir George on Instagram with the caption: "R.I.P. George Martin. I'm so gutted I don't have many words. Thinking of Judy and Giles and family. Love Always, Sean."
Prime Minister David Cameron tweeted: "Sir George Martin was a giant of music - working with the Fab Four to create the world's most enduring pop music."