Mrs Dunwoody entered Parliament in 1966 with husband John
Gwyneth Dunwoody, who has died aged 77, was a principled and independent MP who was born and brought up in the Labour movement.
Born in Fulham, west London, in 1930, she joined the Labour Party at the age of 16, and served as town councillor in Totnes in Devon in the 1960s.
She had impeccable political pedigree: both her grandmothers were suffragettes; and her father - Morgan Phillips - was Labour's general secretary between 1944 and 1962.
Her mother - Norah Phillips - was a life peer in the House of Lords and Lord Lieutenant of Greater London until 1986.
Overtook Barbara Castle
From 1966-1970 Mrs Dunwoody was MP for Exeter, entering Parliament with then husband Dr John Dunwoody, who was MP for Falmouth and Camborne for four years.
In 1974 she became MP for Crewe, which became Crewe and Nantwich in 1983.
In December 2007 she surpassed Barbara Castle's record for the longest unbroken service for a woman MP.
Mrs Dunwoody was also a Member of the European Parliament between 1975 and 1979, at a time when MEPs were nominated by national parliaments.
Her most famous victory over those within the party who would shut her down came in 2001, when backbencher Labour MPs defied the party hierarchy to back her as chair of the House of Commons' powerful transport select committee.
Mrs Dunwoody (5th from right) was in Neil Kinnock's 1984 shadow cabinet
Under her leadership, the committee had produced several unwelcomely frank reports on government transport policies - which many saw as a factor behind the government's desire to replace Mrs Dunwoody with a more pliant chairman.
Described as a peasants revolt against the "control freakery" of Downing Street, dozens of Labour MPs took advantage of a free vote to reject the government's favoured replacement and keep her in the chair.
The Labour MP, Stephen Pound described the government's machinations against her at the time as "a dreadful botched attempt"
He said: "The House rose - as one - you know, to save our Gwyneth."
Mrs Dunwoody always saw herself as a loyal Labour supporter, with unconventionally frank views about "New" Labour, and the values it represented.
In a 2002 interview with the Guardian newspaper she said the party under Tony Blair "appeared to have no principled core."
She added: "It appears to have no very clear idea of its perspectives or its ultimate objectives, and the things that it's done of which I would be very proud, it appears to be ashamed."
The plight of Pooh and friends inspired an appeal from Mrs Dunwoody
At the heart of New Labour's problem, she said lay "a confusion of identity".
For her part, Mrs Dunwoody's identity is best described a staunch and loyal defender, since childhood, of traditional Labour values.
In 1983 Dunwoody stood (unsuccessfully) as a Eurosceptic candidate for Labour's deputy leadership - a position which was increasingly unpopular within the mainstream party, but one she consistently maintained throughout her career.
In was in keeping with her lifelong ability to champion unpopular and sometimes surprising causes.
In 1998, shortly after Mr Blair's election, she managed to hijack the new prime minister's agenda from matters of international weightiness to a dispute over a stuffed toy, during an official visit to see President Clinton in the White House.
Many will miss Gwyneth Dunwoody's independent spirit and compassion
On US television Mr Blair found himself defending the right of a New York museum to retain ownership of a Winnie the Pooh doll - after Mrs Dunwoody publicly appealed for its return to the UK, saying she "detected sadness" in the glass case display.
She leaves behind a daughter and two sons, and 10 grandchildren.
Mrs Dunwoody's death will force an unwelcome by-election at a vulnerable time for the party.
Even though her seat - Crewe and Nantwich - has seen a steadily increasing Labour share since its creation in 1983, much of this was thought to be a personal vote for a principled and unconventional MP.
And in a period when Labour opinion polls are slipping, there is no guarantee Mrs Dunwoody's would-be successor will inherit her support.
Once again, in death - as in life - Mrs Dunwoody's popularity and independence of spirit has helped create a problem for Labour's leadership.