I HAVE been looking again through the inches-thick government papers on the 1976-78 Grunwick strike because they give clues to how Labour governments can respond to big strikes.

The papers show that the police carried out intense political surveillance of the strike. They filed reports full of both detail and absurd rumours — like their fears of trade unionists mobilising hit squads of female plumbers or schoolchildren to cause havoc — which Labour ministers accepted without question.

The Grunwick dispute started when a largely Asian workforce in a north London factory went on strike to support a sacked colleague.

Grunwick processed photographs: this was a big business in the days before camera phones. We all used to send our camera film to factories to be developed, with our holiday snaps coming back in the post.

Grunwick’s “strikers in saris” led by Jayaben Desai were supported by thousands of other trade unionists at mass rallies and pickets.

Future Labour MP Jack Dromey organised much of the support through his leadership of Brent Trades Council, a cross-union support group.

The dispute was a key part of the social unrest of the 1970s, and the final defeat of the strikers in 1978 helped usher in Margaret Thatcher’s Tory victory.

While the unions and left, including many Labour MPs, supported the strikers and said the police were fighting off mass pickets with violence, the Labour government of Jim Callaghan and home secretary Merlyn Rees took a different view.

They wanted Grunwick boss George Ward to compromise, but they couldn’t force him to do so. They viewed the pickets and demonstrators with suspicion.

The file I got under freedom of information was from the Home Office. These were all papers sent to Labour home secretary Merlyn Rees’s office. The papers from the police sent to Rees’s office rely heavily on Special Branch surveillance of the protesters, which was intense.

For every day of picketing and demonstration, the police made notes about every speech, naming the speaker and what they said. They listed every banner and even sometimes every chant shouted out by protesters.

The names of all those involved went into Special Branch files. As we now know, the police also spied on the Grunwick strike by sending officers from the Special Demonstration Squad to live undercover as left-wing activists and report back on plans for Grunwick protests.

The police reports contain a mix of accurate reports and bizarre, alarmist conspiracy theories.

A November 4 1977 Metropolitan Police report on an upcoming Grunwick protest has a lot of detail of what they expect, thanks to this intense surveillance — like noting “a joint 300 contingent of car workers from Dagenham and Luton” is on the way. But some of the predictions are alarmist and absurd.

“Tactics discussed to stop Grunwick’s include: qualified woman plumbers and electricians gaining access to the factory on some pretext this weekend to cut off such supplies.

“The arrival of a group of Yorkshire miners early at the weekend to establish the movement of Grunwick buses and sabotage them at the last moment, if possible early Monday morning in the hope it will be impossible to find a replacement at such short notice.

“If the above tactics fail: a group of miners from Kent and south Wales will try and overturn the Special Patrol Group transit van preceding the Grunwick bus.”

Needless to say, the van was not overturned, and the hit squad of women plumbers and sparkies never arrived. Their phantom existence obviously appealed to some sexist part of the Special Branch unconscious.

But by spreading these scary rumours, the police justified the use of more physical force against the pro-Grunwick protesters.

Another report from November 1 predicts the November 7 picket line, billed as the “day of reckoning,” will be “the most disruptive yet encountered.”

This is because “meetings held in London in connection with this demonstration have been remarkably well attended by young, unemployed student types who have been most forcible in their declaration of support for the strikers.”

Disruptions planned include: “The use of schoolchildren under the auspices of the National Union of School Students to sit in front of police lines until shortly before the coach arrives and then go sit in front of the coach.”

Again, the predicted road blockade of schoolchildren never happened, but did show the police wanted to spread alarmist rumours among themselves and to the Home Office to justify their much-criticised use of force against the protesters.

The reports also show the police always viewed the protests as driven entirely by political groups.

So an October 1977 report says Grunwick protests — which could involve up to 8,000 people — are “divided into various groups.”

These are: “The Grunwick Strike Committee, led once again by Jack Dromey, who is backed by the London District of the Communist Party,” the Apex union, the “ultra left-wing elements of the Socialist Workers Party, International Marxist Group (IMG), and similar organisations,” and finally, “the Asian workers, who are now becoming martyrs of the Indian community.”

The same report notes that “although the IMG anticipates mobilising their full support and can be one of the most vicious groups to encounter on a demonstration, their numbers are small and as many are currently on bail for offences committed earlier, it is unlikely they will take an active role” — which will be a surprise to anyone who remembers the actual IMG from the 1970s.

The effect of these police reports was to encourage the idea that the Grunwick protests were the work of left-wing plotters with wild plans for disruption, not a legitimate movement of thousands of trade unionists. This in turn justified the police to push back as hard as they could.

While Labour MPs complained about police violence against protesters, the Labour home secretary and his ministers appear to have taken everything the police said at face value.

At no point did Labour ministers look at these claims of the attack of an army of women plumbers or the schoolchildren’s sit-down squad and say: “Isn’t this a load of nonsense?”