Ronald Reagan manifestly lived the American dream in which he so fervently believed. He rose from the humblest origins to become a minor Hollywood star, Governor of California for two terms, and finally America's 40th President. His presidency was controversial and marked by some signal failures as well as achievements, but he handsomely won two presidential elections and was one of the few presidents to leave office better loved than when he was sworn in.

As President, he will be primarily remembered for hastening the end of the Cold War - or even, some claim, for winning it. He did this by ordering the largest peacetime military build-up in United States history and by the development of the Strategic Defence Initiative or "Star Wars" programme, which was designed to shield America from incoming missiles.

This policy of "peace through strength" made clear to an economically faltering Soviet Union that the arms race was unwinnable, and two crucial nuclear arms reduction treaties ensued. By the time Reagan left office, the threat of nuclear war between the West and the communist bloc had greatly diminished. Reagan's foreign policy in other areas, however, notably the Middle East and Central America, was far less successful.

Domestically, Reagan's two great achievements were to restore America's pride and confidence after Vietnam, Watergate and the "malaise" of Jimmy Carter's presidency, and fundamentally to change the terms of the political debate by advancing what was, in 1980, the almost heretical notion that government was part of the problem, not the solution. Twenty-four years later, that notion has been embraced by all but the most liberal of America's politicians.

Reagan presided over the longest expansion in the US economy since the Second World War; but it came at considerable long-term cost. He cut taxes, but failed to cut spending, and in the course of his presidency America went from being the world's leading creditor nation to its most prominent debtor, driving up interest rates abroad and bequeathing a huge burden of debt to the next generation of Americans.

The other major blot on Reagan's presidency was the Iran-Contra scandal. With his blessing, US arms were secretly shipped to Iran in an attempt to secure the freedom of US hostages in Lebanon. White House aides then diverted the proceeds from those arms sales to the Nicaraguan Contras, in defiance of a congressional ban on such support. Reagan denied knowing of the diversion, but on this matter he was, for once, not convincing, and in any case he had no answer to the charge of appalling judgment and slack management.

Ronald Reagan had no claim to be considered an intellectual, and for a long time the elites in Washington and other world capitals found it hard to take the former actor seriously. He fell asleep during an audience with the Pope, gave himself a famously light workload, culled jokes and anecdotes from the Reader's Digest and even in interviews tended to be lost without his "cue cards". Once, believing a radio microphone was switched off, he jokingly announced that "the bombing begins in five minutes", and late in his presidency it was revealed that his wife Nancy had consulted an astrologer about propitious dates for major policy ventures.

Yet Reagan brought other talents to the presidency that more than compensated for such shortcomings and eccentricities. He had in view a few basic and immutable goals, which gave his Administration an unusual clarity of purpose - the unleashing of America's entrepreneurial spirit by lowering taxes and reducing the role of government, and the restoration of the United States' international pre-eminence by strengthening its military forces and confronting communism.

He was an uplifting speaker who took over a demoralised country and convinced it that its best days were still to come. He was adept at sensing and articulating the nation's mood, most notably following the Challenger space shuttle disaster of 1986. He restored lustre and dignity to the presidency, but above all he was immensely likeable. Democrats dubbed him "the Teflon President" because no dirt ever stuck to him, and that was perhaps because he was always so genial and optimistic. He also had a fine line in self-deprecating humour. In a farewell speech he said he planned to "lean back, kick up my feet and take a long nap", then added: "Come to think of it, things won't be that different after all."

The publication in 2003 of a selection of his letters, written both in office and in the years before and after, showed him at his best. Whether writing to friends or political opponents, to young children, activists or members of his own family, he showed himself to be principled, witty and thoughtful, even meditative. His religious faith clearly guided him in his attempt to do the right thing, and he remained courteous and considerate to those who opposed him.

On a personal level, however, Reagan was an enigma. He was a friendly man who had practically no close friends except his wife Nancy. He forgot the names of senior officials, and was remote even from his four children, one of whom - Patti, his daughter from his second marriage - openly rebelled against his conservatism. Edmund Morris, his official biographer, once called him "the most mysterious man I have ever confronted. It is impossible to understand him."

Although he lacked close friends, Reagan had an ideological soulmate in Margaret Thatcher, whom he first met in London in 1975 before either of them was in supreme office. While he was President and she was Prime Minister, the so-called "special relationship" between Britain and the US blossomed. Most obviously, he gave Britain vital logistical and material support during the Falklands conflict of 1982. She welcomed the deployment of American cruise missiles on British soil, and in 1986 she allowed Britain to be used as a base for the bombing of Libya. Their one serious argument was over the US invasion of Grenada, a member of the Commonwealth, in 1983, but the last document Reagan signed as President was a letter of appreciation to Baroness Thatcher, and in 1989 he received an honorary knighthood from the Queen.

Ronald Reagan, Mikhail Gorbachev and Margaret Thatcher were the three dominant figures of the 1980s. History may well place the man who was sometimes unkindly called "the acting President" in the first rank of those who have occupied the White House. At the very least he will be one of the most prominent in the second division.