In 1972, 31 pickets were arrested and put on trial in Shrewsbury, 24 were convicted. The Tory government was trying to wreak revenge on striking building workers, after being given a bloody nose by the miners and the dockers.
Severe prison sentences were dished out to six of the pickets. The best known were Des Warren and Ricky Tomlinson, the "Shrewsbury 2." Des died as a direct result of the treatment he got in prison and all 24 were blacklisted after the strike.
Successive governments have refused to clear their name. But the campaign has been revived and is calling for a public inquiry into the prosecutions. They are also demanding the release of government documents from 1972 and 1973 that detail the involvement of the security services, including MI5, in the cases.
Jane James recently interviewed one of the campaigners, Pete Farrell.
It's going to be a hard fight to get a public inquiry. Each time we go to the home secretary Jack Straw, a few more little bits come out but the key points are still secret because of 'national security'.
But now we feel the campaign is going to grow. The next stage will be to take the campaign to Jack Straw's doorstep. The idea is to hold a meeting in Blackburn and launch a very active campaign with stalls on the streets and petitions. We want to approach the unions to provide thousands of leaflets and posters.
We want to walk up and down outside Straw's house. We want to have a press conference where we will challenge him and ask why after 30 odd years all this remains a state secret.
The march in Shrewsbury is going to be an annual event like Tolpuddle and we want the trade unions to sponsor coaches to that every year.
They could have got them out. In 1972 the miners had just defeated the Tory government. They attempted to bring in the Industrial Relations Act to police the unions. It was the first real crisis of capitalism and they attempted to make the working class pay for that crisis.
The Pentonville dockers were arrested and jailed. But with virtually every dock in the country coming to a standstill and 60,000 workers surrounding the prison, they released the dockers.
Sometime after that the engineering union AUEW had its funds seized and was fined. Thousands of people poured out of the factories and threatened a general strike - the employers paid the fine themselves.
The Tory government criminalised the Shrewsbury pickets. They used the 1875 Conspiracy Act, which gave the opportunity to the trade union leaders to run away. Many of them claimed that the pickets had broken the law and all we could do was appeal.
But there was support from trade unionists for all-out action to free the pickets. A march from Wigan to London was supported by thousands of workers in London. But as Des Warren said in his book, the key to his cell lay on the TUC's table, but they never picked it up.
Back in the 1970s there were huge direct labour organisations (DLOs) employed by the councils. Camden had something like 1,200 workers - it was the first DLO to go out in the national strike.
Some sites are organised today but with unelected convenors. The employers are allowing the unions on to the site, the unions get the subs but they tone down the militancy - the so-called sweetheart deals.
There's not as many trade union-organised jobs, but overall there has been a drop in the number of deaths, there were three deaths a week at one time.
I'm the chair of the Construction Safety Campaign (CSC) and we've put a lot of pressure on the trade union leaders to take health and safety issues seriously since it was set up over 20 years ago.
But workers are not just getting killed outright, there's thousands of deaths from exposure to asbestos, dust and chemicals. Many retire and die and they are not recorded as construction deaths.
Workers Memorial Day on 28 April every year was started really by the CSC and the Hazards movement. In London for example it is us who are organising it every year.
But in the last few years more trade unions, including most of the construction unions have become involved. And the campaign is having an effect on government policies.