Chas Newby, a bassist for The Beatles in their early days, has died aged 81.

The musician played a key role in the iconic band’s early success in the 1960s while the group’s original bassist, Stuart Sutcliffe, was away pursuing his art career.

A cause of death has not yet been announced.

Newby was a member of John Lennon’s first band The Quarrymen, and news of his death was announced by The Cavern Club Liverpool — a music venue where The Beatles performed before finding global stardom.

“It’s with great sadness to hear about the passing of Chas Newby,” the venue wrote in a Facebook post. “Chas stepped in for The Beatles for a few dates when Stuart Sutcliffe stayed in Hamburg and latterly he played for The Quarrymen.”

“Interestingly, he was also the first left-handed bass guitarist in The Beatles. RIP Chas Newby thoughts and well wishes from everybody at The Cavern Club,” the post concluded.

Tributes have poured in since the news came to light, with Roag Best, the brother of former Beatles drummer Pete Best rushing to Facebook to pay his respects.

“Both Pete and I and the whole Best family absolutely devastated to hear the very sad news with regards to one of the families closest friends Chas Newby passing last night,” he wrote.

“Many of you will know him for playing bass guitar for both The Beatles and The Quarrymen, but to us he was laid back Chas with the big smile. We’ll truly miss him. Forever in our thoughts. God bless you Chas x.”

Mark Lewishon, a historian specializing in The Beatles, described Newby as a “charming man.”

“RIP Chas Newby, fill-in Beatle and fair chap,” he tweeted. “He deputized for Stuart on a few dates when the Beatles returned from Hamburg the first time, end-1960, including the momentous Litherland date.”

“Latterly he’s been one of the Quarry Men too. A charming man, always a pleasure to meet,” he added.

After stepping in for Sutcliffe in the early 1960s, the band’s frontman Lennon reportedly wanted Newby to continue on with the tour in Germany.

But Newby declined the offer and instead pursued a university degree.

Speaking to the Sunday Mercury in 2012, Newby said he never regretted his decision.

“Music was never going to be a living for me. I wanted to do chemistry,” he told the outlet at the time. “John, Paul [McCartney] and George [Harrison], they just wanted to be musicians.”

“People sometimes don’t believe me when I say I’ve no regrets. But I really haven’t.”