Arctic Monkeys are an anachronism. Damon Albarn, a man who knows plenty about being in iconic rock outfits, claimed that the Monkeys were the last "great guitar band." High praise. Andy Nicholson was a key player in the creation of this great guitar band. The bassist was a founding member of the Arctic Monkeys back in 2002.
The band was originally comprised of Nicholson, drummer Matt Helders, guitarist Jamie Cook and singer Alex Turner. Classic four piece lineup, and the results have subsequently (and similarly) been hailed as classic. Nicholson played bass on the first Arctic Monkeys album, Whatever People Say I Am, That's What I'm Not, but subsequently parted ways with the band despite the album's massive success.
Andy Nicholson was fired from Arctic Monkeys in 2006

Nicholson's parting of ways was a slow process. Arctic Monkeys initially claimed that the bassist was merely going to miss tour dates because of "fatigue." The more time passed, however, the more clear it became that Nicholson was not coming back. He was asked to leave the band, and was replaced by Nick O'Malley.
Matt Helders spoke to Drum Magazine about Nicholson's firing, and he claimed that the two camps simply wanted different things. The drummer stated that the bassist simply didn't enjoy the life that came with touring, and wanted to return to their native Sheffield.
"It’s not for everyone, the traveling, I suppose," Helders explained. "He didn’t get specific. We didn’t want to drag all of that out of him ... We took [Nick] out to America and we just couldn't see going back to the way things were for whatever reason." Alex Turner backed up the drummer's claims, telling the NME that Arctic Monkeys simply wanted to "move forward" without Nicholson.
The bassist is currently on good terms with the band
The story took a more complex, and dark turn when Nicholson appeared on the Michael Anthony Show in 2018. The musician claimed that he was devastated by his firing, and did not feel it was the mutual parting of ways his former bandmates made it out to be. Furthermore, Nicholson described the years following his firing as "soul destroying," and admitted that he contemplated suicide while contending with various mental health issues.
The booming critical and commercial success of the Arctic Monkeys in the decades that have followed Nicholson's firing likely did not help. Fortunately, the bassist has been able to recover. He even told host Michael Anthony that he is currently on good terms with the rest of the band, and confers with them whenever they are in Sheffield.
Nicholson performed in the bands Mongrel and the Book Club following his tenure with the Arctic Monkeys, and he currently serves as one half of the production duo Sticky Blood.