The five musicians began frantically rehearsing, often seven days a week, from lunchtime until about 10 at night. “Only about a third of that time was rehearsing, in the strictest sense of the word,” says the drummer, Terry Chimes. “The rest was asking about what we should like, what we should say, what we should do, what we should dress like, and all the other things. That stuff went on for hours.

“There was a funny sense in which we were trying to sharpen each other up. It was quite wearing. It wasn’t like having fun — it was almost a sense that we weren’t there for fun. Bernie (Rhodes, their manager) was in the background orchestrating the way we looked, what we said, the music, the songs.

“Everything had to be worked on to the maximum so that when we were exposed to the public they were going to go ‘Wow!’ ” Of the musicians it was the guitarist Keith Levene who was the most idealistically rigorous, Chimes says: “He was the most keen on making sure no one got too soft or too weak, the guardian of everyone’s attitude.”

Where did Joe Strummer stand in the endless ideological struggle? Years later, after the end of the Clash, the lead guitarist Mick Jones told the photographer Joe Stevens that Strummer had been “like a father figure” to him. It was an interesting remark, for Rhodes was in a similar paternal position. “Joe referred to Bernie as the headmaster,” Chimes recalls. “Joe’s attitude was that our job was to perform the music, and Bernie’s was to do that business stuff we don’t know about.”

“Joe did have politics, more than Mick,” says Rhodes. “He was very good raw material.”

“Joe had a very idealistic idea of the band,” says Terry Chimes. “He wanted us all to be together. He worked with everyone trying to make everything perfect. This idea that we should be as good as we can get was rife throughout the whole thing.

“I found it wearing. I thought being in a band would mean you would drive round in fancy cars and have lots of girlfriends and lots of fun. They thought this was a shocking attitude.”

He laughs. “We’d have arguments, but it would all be theoretical, hypothetical and a bit pointless. It was part of the process of indoctrination we did on each other that we were going to be the greatest band in the world.”

To assist them in this Rhodes sent Strummer for singing lessons with Tona de Brett, a vocal coach who was to train Johnny Rotten, Chrissie Hynde and Billy Idol. “I couldn’t do much for that Mr Strummer,” she said later.

As yet the band had no name. Several had been tried out, among them the Mirrors, the Phones and the Outsider (Chimes insists it was Outsider in the singular — The Outsider, Colin Wilson’s celebrated 1956 study of disaffection, was prominent on the Rhodes reading list). Two that stuck more readily with the five musicians were the Heartdrops, a reference to a Big Youth song title, Lightning Flash (Weak Heart Drop), and the Psychotic Negatives.

It was the bass player Paul Simonon who noticed how frequently the headlines in the London Evening Standard carried the word “clash”. “I didn’t just stumble upon it,” he says. “We were so highly attuned to what we needed by then that the word leapt out at me from the pages of the paper.”

Which was just as well, as — after nagging Rhodes ceaselessly — the group had their first gig booked, as support act to the Sex Pistols at a pub called the Black Swan, 180 miles up the M1 in Sheffield, on July 4, 1976. Strummer’s equipment included a microphone he had stolen from the English National Opera House when he had worked there as a cleaner.

“(The gig) was pretty good,” Strummer said afterwards. “There we were in Sheffield and I think it was on a Sunday afternoon and all these people came out of the woodwork, you know, like punk types: ex-Roxy Music, the leopard-skin period, but searching for the next thing. Lots of make-up and hair beginning to go berserk.

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