Obituary: Her downfall was a mixture of skulduggery among some of her colleagues, and a fear among others that people were getting bored with her to the extent that they would vote anti-Tory at the next election just to see a fresh face in power.
There were tears visible in her eyes as she was driven away from Downing Street for the last time after 11 years as prime minister to hand in her seals of office to the Queen.
Some days later, the Queen appointed her a member of the Order of Merit and her husband, Denis, was made an hereditary baronet. She was “deeply honoured” for her own part and “thrilled and delighted” for Denis.
But she insisted then that she wished to remain plain Mrs Thatcher.
It was not long, however, before she entered the House of Lords. She seemed incapable of living without some confrontational forum in which to operate.
And there was no diminution to her style. It was as fiery, unequivocal and straightforward as ever. Her ardour was undimmed and her contributions were no less full-blooded than ever they had been.
She was an extraordinary woman, who never understood why the Tories had discarded her. And she found life virtually impossible to live without a battle to fight - and to win.
Mrs Thatcher summed up, with remarkable prevision, her own beliefs three years before she became prime minister and just after the Kremlin had dubbed her - flatteringly, she thought - the Iron Lady.
She told her audience: “I stand before you tonight in my green chiffon evening gown, my face softly made up, my fair hair gently waved . . . the Iron Lady of the Western World? Me? A cold war warrior? Well, yes - if that is how they wish to interpret my defence of values and freedoms fundamental to our way of life.”
Although Margaret Thatcher normally enjoyed robust health, she suffered one or two setbacks along the way. She was taken ill briefly once in Sri Lanka, damaged her ankle during a fall at a Conservative Party conference in Bournemouth, and suffered a minor stroke while on holiday with Sir Denis in Madeira late in 2001.
But she bounced back from all these setbacks. And in March 2002, she published her latest book, Statecraft.
It was around this time that her doctors told her that she must make no more public speeches, an instruction which she did not obey to the letter.
Then she suffered a devastating blow in June, 2003 when her husband, Denis, died after a short illness. He had seemed to have recovered from a six-hour heart bypass operation he had undergone some months earlier.
At the subsequent funeral service, Lady Thatcher looked frail. At that time, stories started to emerge that she was losing her short-term memory and easily becoming confused. But she continued to attend the House of Lords from time to time.
It looked as though it was going to be a sad end to the life of such a powerful, decisive, fearless and honourable woman. However, her health appeared to improve after a visit to South Africa, and she started to make more regular appearances in the House of Lords.
Meanwhile, the 25th anniversary, in May 2004, of her accession to Downing Street as Britain's first woman prime minister, was celebrated with a lavish dinner at London's Savoy Hotel at which, defying doctors' orders, she spoke robustly, attacking the Blair government and praising Michael Howard, the new Tory leader.
A year later there was to be another such occasion, this time at the Dorchester, to mark the 30th anniversary of her election as Tory leader in 1975.
But amid all these celebrations, there was a new and unpleasant shock for Lady Thatcher on the horizon: the arrest in South Africa on August 25th, 2004, of her devoted son Sir Mark Thatcher, who was charged later with contravening two sections of South Africa's Foreign Military Assistance Act which bans residents in that country from taking part in any foreign military activity.
The charges related to “possible funding and logistical assistance in relation to an attempted coup in Equatorial Guinea” organised by Thatcher’s friend Simon Mann.
Ultimately, to huge relief all round, following a process of plea bargaining, he pleaded guilty to the less serious charge of investing in an aircraft (used in the unsuccessful coup attempt) without making proper investigations into what it would be used for.
He was fined three million rand (about €288,484) and received a four-year suspended jail sentence.
In June 2004, Lady Thatcher attended the funeral service in Washington of her "dear friend" Ronald Reagan. In a moving, pre-recorded tribute, she said: "We have lost a great president, a great American and a great man. And I have lost a dear friend."
And in February, 2007, Lady Thatcher became the first ex-prime minister in history to have a statue of herself unveiled in the House of Commons while she was still alive.
At the ceremony, the Iron Lady said: “I might have preferred iron, but bronze will do. It won’t rust and this time, I hope, the head will stay on.”
This was a reference to the fact that some years earlier a political activist had decapitated a marble statue of her on loan to London’s Guildhall.
Then, shortly after Gordon Brown - who had earlier praised Lady Thatcher as a "conviction politician" - became prime minister in June, 2007, he invited her into Downing Street, an event which created anger in some sections of the Labour Party.
But this was exactly what Tony Blair had done ten years earlier, soon after he entered Number 10.
There was another health scare in March, 2008. Lady Thatcher had succumbed to the heat at a dinner in the House of Lords, and fainted. She was taken to nearby St Thomas’s Hospital for tests, but allowed to go home the following day.
And then in the late spring of 2009, she fell and broke an arm. She underwent an operation to have her arm pinned.
PA