A CONSPIRACY could be as subtle as a ‘nod or a wink’.

So said the judge in the 1973 trial that saw six of the ‘Shrewsbury Pickets’ – including Liverpool actor Ricky Tomlinson – jailed for their part in the builders’ strike of the year before.

Now, 40 years later, the pickets have learned that crucial government documents will not be released for another 10 years in the interests of ‘national security’.

Justice Minister Chris Grayling said the reasons for the files being witheld remained “valid”.

Mr Tomlinson and his fellow campaigners are of the view that there was indeed a conspiracy going on – but not in the meeting rooms of trade unions but in the corridors of Whitehall.

The thousands of historical government papers dug out from the national archives at Kew by campaigning researcher Eileen Turnbull, with their ‘top secret’ markings, could easily be the props of a Cold War spy novel.

It was the early 1970s, one of the most volatile periods of government-industrial relations the country has ever known, with builders, miners and dockers striking and car plant workers on the verge. Heath government files at Kew suggest up to 35,000 known Communists may have been active within the trade unions, including from the International Marxist Group.

Mr Tomlinson, although a union activist, couldn’t have been further from Communism in September 1972 when the pickets travelled to Shrewsbury.

“I was a right-winger at the time, and I must have come from one of the most right-wing families in the country,” he told the Post.

“I was asked to be a prosecution witness in the first place, and when I refused that’s when they said they would have to charge me.”

Now 73, Mr Tomlinson believes it was his part in the relatively minor builders strike that made him and the pickets the ideal target for the powers-that-be bent on quelling the power of the unions. To have gone for the miners or dockers in such a way, he and Mrs Turnbull contend, would have seen the whole country down its tools.

But if the establishment wanted to send a message, the criminal justice system was less keen.