The announcement of what will be a hugely symbolic event came as Mikhail Gorbachev ended a packed 36-hour visit with an informal lunch with the Queen amid the splendour of Windsor Castle. It confirmed both the close personal and political relationship between himself and Margaret Thatcher, and their different views on nuclear deterrence - above all on the need for Nato to modernise its short-range nuclear missiles in Europe.
After what Mrs Thatcher described as a truly remarkable visit by "a man of destiny", she said there was no question of getting rid of nuclear weapons. The modernisation programme would go ahead, and Mr Gorbachev's announcement on the curtailment of Soviet production of weapons-grade uranium would "have no effect in practice".
Speaking at the airport before his return to turbulent domestic politics, and indications of new nationalist unrest in Georgia, Mr Gorbachev proclaimed his "great satisfaction" with what had been achieved in London. But he warned that, if Nato went ahead with plans to modernise, it would jeopardise the Vienna talks on European co-operation, and "devalue" the gains of the Intermediate Nuclear Forces (INF) Treaty. "We strongly oppose modernisation . . . nor do we intend to modernise our weapons unless we are forced to do so," he declared.
Last night, Gennady Gerasimov, the Soviet spokesman, rejected suggestions that Mr Gorbachev's speech, which contained no hint of widely expected new proposals on Europe, had been a disappointment. "You in Europe have become too pampered," he said, blaming the West for not responding to initiatives already tabled by Moscow.
Mr Gorbachev did, however, aim his words as much at the Soviet public as at his international audience. For all its problems, perestroika was irreversible. "This is only the beginning of the road for us." Tests and trials lay ahead, "but we have chosen definitively and irrevocably the route to new forms of life".
As well as the announcement of an end to Soviet production of enriched weapons-grade uranium, and the closure of plutonium reactors, Mr Gorbachev disclosed that total Soviet troop strength at the start of this year was only 4.3 million, well below Western estimates of 5.1 million or more.
After implementation of the unilateral cuts of 500,000, announced last December, Mr Gorbachev claimed that Soviet troops would number 3.76 million in all, compared with a US strength of "more than three million" and a navy more than twice the size of Moscow's: "Fears of the `Soviet military threat' are groundless." Mrs Thatcher, who was invited to make a return visit to Moscow, said she was very happy at the prospect of a state visit by the Queen: "There will be tremendous advantage; it will indicate the warmth in the relationship."
But the most positive line taken by Mrs Thatcher was her fierce support for the process of perestroika. She said that, following his political reforms, Mr Gorbachev had turned to the more difficult task of economic reconstruction in a country which had not had a free market for 70 years.
As for the main Gorbachev initiative of the day, Mrs Thatcher said that the Soviet Union already had a "sufficient" stockpile of uranium, which would increase as SS20s and other missiles were dismantled. She repeated her view on nuclear deterrence, saying: "Strong and sure at the moment means also nuclear." On Nato modernisation of short-range weapons, Mrs Thatcher said: "Obsolete weapons do not deter . . . The Soviet Union has just completed its programme of modernising short-range nuclear weapons. We have not yet started upon ours. I think we should complete it."
Front-page story from `The Independent', Saturday 8 April 1989