Domestic politics in the United Kingdom for decades to come were shaped by it and the country’s position in the world determined by it.
Yet files released today by the National Archives show the deal struck in 1980 between Mrs Thatcher and the then US President Jimmy Carter for Britain to buy the Trident submarine-launched missile system to replace the UK’s ageing Polaris deterrent was opposed by no fewer than two-thirds of her Conservative cabinet.
The revelation is extraordinary, for it shows that senior Tories, including the then defence secretary John Nott, and some of the defence chiefs, had concerns over the cost of the procurement, something the electorate had little or no idea of at the time while the government collectively gave the impression, in public at least, of steely Churchillian resolve.
It is a truism to say that it is not possible to alter the course of history, but it is fascinating to speculate on what might have been had the voters of that time know what we know now. Would the Thatcher government which, we should remember, was by no means secure in its early years, have survived had the fundamental internal divisions been uncovered? And would the outcome of the 1983 election, which Labour went into committed to unilateral nuclear disarmament, have been the same? We cannot tell but we can at least ponder and reflect.