SHOP steward Gerry Ross takes part in what looks like a tense conversation with a security guard at John Brown's shipyard in Clydebank in 1971, as two workers look on.

Even 40 years on, the mention of the initials of the company involved – UCS – are enough to recall memories of one of the key events of the 1970s.

The dispute centred on the future of Upper Clyde Shipbuilders. The combine had been put together in the late 1960s when the Labour Government, trying to address the decline in shipbuilding orders, recommended five yards on the Upper Clyde be merged. The five were Fairfield's, Stephen's, Connell's, Yarrow and John Brown. Yarrow and Connell's were the only ones that were making a profit.

Yarrow joined on the basis of 51% owned by the consortium and 49% owned by Yarrow & Co.

But by June 1971, Yarrow's had been allowed to return to independent work – and a liquidator was appointed in relation to the rest of the business.

The Tories, who had won power in 1970 under leader Ted Heath, were strongly disinclined to dig deeper into the public purse to fund what they saw as a lame duck.

But the men on the Clyde were equally strongly disinclined to accept the sentence of death that had been passed on the yards and that 8500 jobs would disappear.

Their solution was not to down tools and go on strike but, instead, to stage a work-in to demonstrate that the yards were still viable. Jimmy Reid, one of the shop stewards who would become famous through the work-in, made the workers' feelings clear when he said the Upper Clyde "was being sacrificed on the altar of political dogma".

In a speech that helped make his name, he told the workers: "This is the first campaign of its kind in trade unionism. We are not going on strike. We are not even having a sit-in. We are taking over the yards because we refuse to accept that faceless men can take these decisions.

"We are responsible people and will conduct ourselves with dignity and discipline. There will be no hooliganism. There will be no vandalism. There will be no bevvying, because the world is watching us. "We are not wildcats. We want to work ... we don't only build ships on the Clyde, we build men. They have taken on the wrong people, and we will fight."

The work-in famously attracted the support of such celebrities as former Beatle John Lennon, whon sent a cheque for between £5000 and £10,000 to the men, and Billy Connolly, a former shipyard worker beginning to make a name for himself in showbiz. Many Scottish business people also voiced their backing. In the end, the Tory Government caved in and performed a spectacular U-turn. The yards and the jobs were all saved but their long-term future was not guaranteed.