Margaret Thatcher secretly considered the use of troops to break a strike by coal miners, according to newly released government papers.
Documents released by the National Archives at Kew, west London, show the extent of the planning by Mrs Thatcher's Conservative government for the decisive showdown with the miners which helped define her political legacy.
The papers show that ministers and officials repeatedly warned that a confrontation with the National Union of Mineworkers (NUM) and its leftwing leader, Arthur Scargill, was inevitable.
Mrs Thatcher, who had been a minister in Edward Heath's government in the 1970s when it was brought to its knees by a miners' strike was only too well aware of the stakes involved.
In February 1981 - less than two years into her premiership - she had been forced to cave-in to the NUM's pay demands, aware that the Government was unprepared to withstand a prolonged conflict.
Behind the scenes, however, a secret Whitehall working group - codenamed MISC 57 - was established to lay the ground for the battle to come.
Plans were set in train quietly to purchase land next to electricity power stations - which were nearly all coal-fired - so that coal could be stockpiled to keep them running through a strike.
They also began the expensive process of converting stations to dual-firing so that they could run on oil if coal supplies were exhausted.
MISC 57 also discussed using troops to move coal stocks, although officials were unenthusiastic warning that it would be a "formidable undertaking".
In a memorandum dated October 27 1983, PL Gregson at the Cabinet Office noted: "To move 1/2 million tonnes of coal per week - twice as much as was transported by road during the rail strikes earlier this year, when power stations were not picketed - would involve 4-5,000 lorry movements per day between pitheads and power stations continuously for 20 weeks.
"The law and order problems of coping with pickets not just at the power stations but also at the pitheads would be enormous and would arise from the very outset of the strike.
"A major risk might be that power station workers would refuse to handle coal brought in by servicemen in this way."
The following day, however, a meeting of senior ministers chaired by Mrs Thatcher ruled - while they might be able to rely on existing coal stocks in the early stages of a strike - planning for the use of troops should continue.
"It was agreed that ... it might be necessary at some stage to examine more radical options for extending endurance, including the use of servicemen to move pithead stocks to power stations by rail and road," the minutes noted.
As the Government moved towards the general election of 1983, preparations for an expected conflict over its programme of closing pits considered uneconomic was stepped up.
In January 1983, Energy Secretary Nigel Lawson said while the National Coal Board (NCB) was still not yet confident of winning a strike, they needed to be ready for a decisive showdown once the election was out of the way.
"While the Board are currently thinking a national strike would last for two months, I believe it could well be longer. We would certainly need to be prepared for it to be longer," he wrote in a memorandum to Mrs Thatcher.
"If Scargill succeeds in bringing about such a strike we must do everything in our power to defeat him, including ensuring that the strike results in widespread closures."
His view was echoed by John Vereker, a member of Mrs Thatcher's policy unit who also served on MISC 57, although he was far from sanguine about the outcome.
"The Department of Energy and the Treasury now acknowledge what John Hoskyns (head of the policy unit) argued from the day he arrived here; that sooner or later the Government would have to face, and win, a major national coal strike," he noted.
"It does seem considerably less likely that we could bring the Coal Board anywhere near breakeven without winning a strike, and that of course carries the major risk that embarking upon and then losing a strike is the most expensive option of all."
Two months later, however, in a memorandum dated March 11 1983, he was much more optimistic.
"I am happy to report that this morning we for the first time glimpsed on the horizon the prospect of indefinite endurance, albeit at a very considerable cost for converting the main coal fired power stations to dual firing," he wrote.
"There is some way to go, but it looks as if we can achieve nine months of endurance at very little cost on top of what we have already incurred: and twelve months' endurance at an additional cost of £70 million for further coal stocking capacity."
There was a further step change in preparations that February with the appointment of Ian MacGregor as the new chairman of the NCB.
The American came with the reputation of a hatchet man, having been credited with turning round the ailing British Steel, with the loss of half the workforce.
Nicholas Owen on MISC 57 said that it was the opportunity to put forward "more ambitious objectives" for the pit closure programme than those Mr Lawson had been working on.
"In view of the importance of this appointment, the Prime Minister may wish to either discuss the objectives with him herself, or to register her interest in hearing of his reactions to them," he wrote.