Tony Benn was for decades the most independent-minded, powerful and passionate voice of the hard-left at Westminster, and the man whose crusading zeal led to the new law which allowed him to renounce his own peerage and return to the House of Commons.
There was no one else in his era who so superbly and with such fire led the left and who so utterly ignored his own personal prospects in order to get his message across.
He served in Harold Wilson's cabinets, but was a constant thorn in the then prime minister's side and more than once came within a touch of resignation or dismissal.
Benn was contemptuous of the Labour leadership under Neil Kinnock, and himself made more than one challenge for the post.
And when, after 18 years in opposition, Labour was swept to power in 1997 under Tony Blair's leadership, this was still not the Labour Government of which Benn had dreamed.
It was, without doubt, the most right-wing Labour Government in British history, and Benn found very little in its policies to appeal to his pure socialist inclinations and instincts.
He was, for instance, furious over the "immoral" bombing of Baghdad in December, 1998, and must have been bitterly disappointed that a Labour Government, after all those years in the wilderness seemed, in his eyes, to lack the main ingredient, namely socialism.
But although he was unpopular with the Labour hierarchy he remained the darling of the rank and file right into his old age.
He was uncompromising in his views which he distilled with passion and above all clarity, and he probably commanded more popular support among Labour voters than most other leading figures in the movement in his era.
However, in 1999, Benn announced at the age of 74, that he would not be fighting his seat in parliament again. But he insisted that this was by no means retirement from the political battle, in a way it was the reverse of that.
He said he would be able to continue - indeed intensify - his political activity outside the House for the remainder of his life, which he predicted would continue until he was at least 100 years old.
No one before had quit parliament in order to practise politics even more fervently outside Westminster than he had done within it.
Benn fulfilled that pledge by not standing in the 2001 general election and, true to his word, his "retirement" enabled him to "spend more time with politics". Even though no longer an MP, Benn was regularly seen inside the Palace of Westminster as busy as ever in pursuit of the causes which were so dear to his heart.
He also broke new ground for "retired" politicians, appearing on the stage in provincial theatres around the country, sitting at a table, with a huge mug of tea and a pipe and dissertating on politics and engaging with his audience on political issues. Invariably, the "House Full" notice appeared outside the theatres where he was performing.
Benn was the reluctant peer - Viscount Stansgate - who was barred for a time from the House of Commons after winning a seat at Bristol because his peerage made him ineligible.
It was then that he embarked on a battle royal - in which he was victorious - to enable inheritors of peerages to renounce them if they wished. It was this legislation which enabled Lord Home to renounce his peerage and to become prime minister.
But his refusal to be budged from the line he chose, made him many enemies throughout the Labour Party. His was often a lone or minority voice in the party's ruling National Executive, but he never gave in without a bitter struggle.
His diaries were a veritable Aladdin's Cave of the political history of the period. Every night, without fail, he completed a diary - in the latter years on a tape - of the day's events.
And he had an obsession that his words would be distorted by the press. That is why he taped every interview that he gave.
Tory cabinet minister Michael Heseltine summed him up brilliantly: "There is something manic about him, but he has the persuasiveness of someone who has worked it all out to his satisfaction.
"He has these extraordinary theories into which he can fit all the facts, and this gives him a great flow, like a huge river which is unmistakably coming from somewhere and going somewhere, but the longer you listen, the more you realise he is trying to push water uphill."
Benn was renowned as a prodigious tea-drinker, and his desk - whether in government or opposition - was invariably laden with the largest mugs that money could buy.
Anthony Wedgwood Benn was born on April 3, 1925. But he always wanted to be known purely as Tony Benn.
And although he once claimed in Who's Who to have been educated in "the university of life", he actually attended Westminster School and New College, Oxford. He was president of the Union in 1947.
During the war, Benn served as a pilot with the RAF and Fleet Air Arm, being awarded the DSO and the DFC.
He joined the Labour Party in 1943 and entered the Commons as MP for Bristol South East in 1950. That was the beginning of a tempestuous political career, somewhat belittled by the fact that many of those around him occasionally mistook the fervour of his argument for irrationality of mind.
The impression remained throughout his life, even among many of his supporters on the left, that he was somehow less than the sum of his formidable parts.
He assumed also that he was always on the side of the angels. "I have had the advantage," he once solemnly told electors, "of a radical Christian upbringing". He campaigned loud and long for the disestablishment of the Church of England.
Benn remained active throughout the 1950s, and before the end of the decade he was already an active member of the national executive and the shadow cabinet.
But the death of his father, Viscount Stansgate, in 1960, forced him to quit the Commons as he automatically inherited the title. He fought and won the subsequent by-election having declared that he disclaimed the viscountcy, but was physically barred from entering the Commons. The Tory runner-up was awarded the seat.
It took him three gruelling years in the political wilderness to secure an Act of Parliament to make a disclaimer legally enforceable. The Tory MP for Bristol South East stepped down as promised, and Benn was re-elected.
And when Labour returned to power after 13 years in opposition, he became postmaster general in 1964 and launched GIRO a year later. He also campaigned unsuccessfully to have the Queen's head removed from postage stamps, and on one memorable occasion at the Palace he knelt on the floor and spread stamp designs in front of her.
But Benn, typically, made a huge issue out of this. He said later: "If the Queen can reject the advice of a minister on a little thing like a postage stamp, what would happen if she rejected the advice of the prime minister on a major matter?
"If the Crown personally can reject advice, then, of course, the whole democratic facade turns out to be false."
This protest epitomised what Benn stood for throughout his political life: the massive patronage afforded to a prime minister through the Crown.
In March, 1966 he became minister of technology. When he moved to technology, the Queen told him: "You'll miss your stamps."
According to some reports, Benn was pleased at Labour's defeat in 1970 because, it was said, it gave him the opportunity to try to steer Labour and its leaders leftwards. But his endeavours had little effect.
On resumption of power, Benn was made industry secretary in 1974, but after advocating government funds for co-operatives at Meriden motorcycles, Wilson demoted him to energy secretary.
He was constantly having run-ins with Wilson, who was getting more and more unhappy about Benn's individualism and what were regarded as cranky ideas. Later, Benn was to say: "In the end, the tragedy of Wilson was that you couldn't believe a word he said."
For his part, Wilson said of Benn: "He immatures with age."
In 1981, Benn was narrowly beaten by Denis Healey for the deputy leadership, but he carried on a bitter fight against what he regarded as a witch-hunt against militants in the Labour Party.
However, in 1983, after an unfortunate (for him) carve-up of the constituencies in Bristol, Benn lost his seat in the Commons. But, a year later, with the resignation of Eric Varley from the Commons, Benn was returned as MP for Chesterfield.
Advancing years did not dim his enthusiasm. He mounted "socialist" conferences in Chesterfield, to which all strands of opinion - even those much farther left than himself - were invited.
He openly supported the miners during the 1984 strike, including urging consideration of a general strike in support of the miners.
He condemned Kinnock for his "consistent failure" to support the socialist struggle outside parliament while watering down Labour's basic policies.
And in 1988, he mounted another challenge to the leadership - again unsuccessfully.
Tony Benn has left far more than a pinprick on history. He has left scars on many of his contemporaries who tried in vain to lead this unruly politician and to divert his endeavours and views - many of them regarded as heretical - into legitimate Labour channels.
He suffered from hearing trouble in the wake of a 1981 nervous illness, diagnosed as Guillain-Barre Syndrome, which sometimes left him - he complained - walking like a drunk, although he was a strict teetotaller.
Benn denied stories about his "wealth". One report said his late wife Caroline's American family left money for their four children, and that there was a £200,000 family trust.
He said these reports were untrue although he consistently declined to correct them.
Benn collapsed at the Labour Party conference in Brighton in September, 2005, but after spending two nights in hospital he was fitted with a pacemaker and quickly resumed his political activities.
He is survived by four children. His beloved wife Caroline, who supported him throughout his tempestuous political career died late in the year 2000, after fighting a brave battle against cancer.
Benn was hugely proud of his son Hilary - by no means a Bennite - who became Labour MP for Leeds Central in 1999.
There were tears in the eyes of Tony Benn when, as one of his sponsors, he accompanied his son into the chamber for the first time to take the Oath. Hilary Benn later was to join the cabinet as secretary of state for international development, and later became environment secretary.