Details of Westland row that sparked rift to be revealed

Minutes of an explosive Cabinet meeting which precipitated one of the most serious political crises of Margaret Thatcher's premiership are to be released early, the Information Commissioner's office has ruled.

After a long delay, the Deputy Commissioner Graham Smith has decided that the public should not have to wait for the usual 30 years before finding out who told the truth about the meeting. But he may yet be overruled by the Justice Secretary, Jack Straw, in case it sets a precedent for more recent Cabinet discussions, such as the one that preceded the decision to go to war in Iraq in 2003.

The Cabinet meeting of 9 January 1986 was dominated by a clash of egos between the two strongest characters in the Government, Margaret Thatcher and her Defence Secretary, Michael Heseltine. When Mr Heseltine was told, in coded language, that he was banned from giving his side of the argument to the press, he gathered up his papers, walked out, and announced that he resigned from the Government. As a backbench MP, he continued to be Thatcher's most dangerous enemy and played a pivotal role in her downfall, before becoming Deputy Prime Minister under John Major.

"The release of this information would help to remove uncertainties and controversies over the historical events surrounding the public resignation of a senior government minister," Mr Smith said yesterday.

The dispute concerned a Cornwall-based company called Westland, which was the only British manufacturer of helicopters. It ran into financial trouble in 1985, and Mr Heseltine tried to arrange for it to join other British, French and German manufacturers in a conglomerate. The Westland board preferred an offer they had received from the US firm Sikorsky. Mrs Thatcher and the Trade Secretary, Leon Brittan, backed the American option.

The battle was fought in private meetings between ministers and civil servants and leaks to the press until the Cabinet met on 12 December, when Mr Heseltine tried to raise the matter, but was cut short by Mrs Thatcher. As a concession to Mr Heseltine, the issue was placed on the agenda for the next Cabinet meeting. But by the time the Cabinet met, Mrs Thatcher's relations with Mr Heseltine were already past breaking point. Too many details of the row were being leaked to the press for her liking, and she issued an instruction around the Cabinet table that all answers to journalists' questions about Westland were to be channelled through the Cabinet Office. At this point, Mr Heseltine erupted.

He has always maintained that he, not Mrs Thatcher, was the true victim of poisonous spin doctoring. Soon after his resignation, Mr Brittan admitted that an official in his department had been told to leak part of a government document to undermine Mr Heseltine's case. Mr Heseltine suspected that Mrs Thatcher's press secretary, Bernard Ingham, was responsible. Mr Ingham has always denied it. Mr Brittan resigned from the Cabinet but was given a knighthood and a job as a European commissioner.

Cabinet in crisis: How they saw it

"It is never easy to persuade those who think that they know how government works... that misunderstandings and errors of judgement do happen, particularly when ministers and civil servants are placed under almost impossible pressure, as they were by Michael Heseltine's antics."

Margaret Thatcher, The Downing Street Years

"What seems beyond any doubt is that those on the Prime Minister's staff – and answering directly to her in No 10 – were responsible for encouraging the leaking of a selective and misleading quotation... in order to discredit a senior colleague."

Michael Heseltine, Life in the Jungle – My Autobiography

"If there was a conspiracy... the conspirators forgot to include me in it. There was no conspiracy. There was no Westlandgate."

Bernard Ingham, Kill the Messenger