Newly-released documents show how the government was keen to cover up spying by the security services during the 1984-5 miners strike.
Secret surveillance was used to track down funds held by the National Union of Mineworkers (NUM) during the year-long dispute.
A legal case to seize the cash was nearly withdrawn over fears that the involvement of security officials would be revealed in court.
Cabinet papers released today under the 30-year rule show that Tory Prime Minister Margaret Thatcher was warned that the press were “sniffing round the story.”
Ministers were concerned that it would be hard to justify the use of “information obtained by interception” in a bid to seize miners’ cash.
Details of secret meetings where an unnamed security services officer was present had been disclosed to lawyers in Ireland, where accountants were trying to seize the money.
Cabinet secretary Robert Armstrong met Mrs Thatcher, the Attorney General and the Home Secretary, and it was agreed that “it was of the utmost importance that no information should be given either in the court in Dublin or in the House of Commons or elsewhere in London about these contacts.”
The 1985 papers also reveal a triumphant note by a Tory advisor to Mrs Thatcher on the dispute.
David Hart’s paper, titled ”The last push”, said: “Like the snow, the last few weeks of the strike must be endured bravely.
“We are on the brink of a great victory. If we don’t throw it away at the last moment. Much greater than the Falklands because the enemy within is so much harder to conquer.”