Regarded as one of the most significant Labour Party politicians, Castle developed a close political partnership with Prime Minister Harold Wilson and held several roles in the Cabinet.

In the latter role, she proved an effective reformer, overseeing the introduction of permanent speed limits for the first time on British roads, as well as legislating for breathalyser tests and compulsory seat belts.

In the latter role, Castle fiercely advocated the passage of the In Place of Strife legislation which would have greatly overhauled the operating framework for British trade unions.

Upon Labour's return to power after the 1974 election, Wilson appointed Castle Secretary of State for Social Services, during which time she was responsible for the creation of Carer's Allowance and the passage of the Child Benefit Act.

[2] Her older sister, Marjorie, later became a pioneer of the Inner London Education Authority, while their brother Tristram (almost always called Jimmie) engaged in field work with Oxfam in Nigeria.

[2] Although her father was prohibited from formal political activity because of his role as a civil servant, he became editor of the Bradford Pioneer, the city's socialist newspaper, after William Leach was elected to Parliament in 1935.

Castle was elected to St Pancras Metropolitan Borough Council in 1937 (where she remained until 1945), and in 1943 she spoke at the annual Labour Party Conference for the first time.

[2] Throughout the Second World War she worked as a senior administrative officer at the Ministry of Food and she was an Air Raid Precautions (ARP) warden during the Blitz.

Castle had secured her place as a parliamentary candidate through the women of the Blackburn Labour Party, who had threatened to quit unless she was added to the otherwise all-male shortlist.

[9] Immediately upon her entering the House of Commons Castle was appointed Parliamentary private secretary (PPS) to Stafford Cripps, President of the Board of Trade,[9] who had known her as a member of the pre-war Socialist League.

[13] Castle entered the Cabinet as the first Minister for Overseas Development, a newly created ministry for which she, alongside the Fabian Society, had drawn up the plans.

[18] The financial commitments of the ministry were omitted from the report, after a protracted clash between Castle and her cabinet colleagues James Callaghan (Chancellor of the Exchequer) and George Brown (Secretary of State for Economic Affairs).

[17] Castle grappled with Callaghan and Brown over the department's budgetary allocation; they reached a compromise following Wilson's intervention,[20] but the sum only amounted to a small increase in spending.

[21] Initially reluctant to head up the department, Castle accepted the role of Minister of Transport (23 December 1965 – 6 April 1968) in a Cabinet reshuffle after Wilson proved persuasive.

[29] Castle urged New York's Transport Commissioner to adopt the same policy, describing plans for more roadways as "self-defeating", stating the solution was "more and better mass transit systems".

She presided over the closure of approximately 2,050 miles of railways as she enacted her part of the Beeching cuts—a betrayal of pre-election commitments by the Labour party to halt the proposals.

[31]) Despite her lack of a driving licence,[2] she attracted controversy when she told local government leaders to give added emphasis to motor vehicle access in urban areas, as "most pedestrians are walking to or from their cars.

This also involved a major cabinet split, with threatened resignations, hot tempers and her future nemesis James Callaghan breaking ranks to publicly try to undermine the bill.

The Conservative Party, led by Edward Heath, enjoyed a surprise victory, despite opinion polling indicating a steady lead for Labour in the run-up.

[35] Castle privately blamed complacency within Labour for their loss and had expressed scepticism about their poll lead, writing in her diaries: "I have a haunting feeling there is a silent majority sitting behind its lace curtains waiting to come out and vote Tory.

When she was attacking the Conservative bill, the government simply pointed to her own white paper, following which Wilson reshuffled her first to the health portfolio and then out of the shadow cabinet.

Despite having been on the Labour back benches since 1972 and not part of the shadow cabinet, in 1974, following Harold Wilson's defeat of Edward Heath, Castle became Secretary of State for Social Services.

Castle recorded in her diary and in her subsequent autobiography that Wilson summoned her to Downing Street where he angrily accused her of disloyalty and that, as he had brought her back into the cabinet against others' wishes and advice, he deserved better from her.

Although he left Wilson's Cabinet virtually unchanged, he dismissed Castle almost immediately upon taking office, in the midst of a complex health bill that she was steering through the House of Commons at the time.

[47] Although he had not yet decided on her successor at the time he fired her, Callaghan removed her under the pretext he wanted to lower the average age of his Cabinet,[48] which she regarded as a "phoney reason".

[55] She remained active in politics up until her death, attacking the then Chancellor, Gordon Brown, at the Labour party conference in 2001 for his refusal to link pensions to earnings.

"[22] Referred to disparagingly by fellow Labour MP Gerald Kaufman as "the Norma Desmond of politics [...] always ready for her close-up",[8] she was noted for always paying particular attention to her appearance.

[8][63] Former Labour leader Neil Kinnock recalled she was distraught when her hairdresser cancelled before a television appearance;[61] in response, Castle said: "If you're a woman in the public eye, getting your hair nice is a constant preoccupation.

[65] Several women politicians have cited Castle as an inspiration for embarking on their careers, including Shadow Foreign Secretary Emily Thornberry,[66] Tulip Siddiq, and former Conservative MP Edwina Currie.

[67] She was commemorated on a postage stamp issued as part of the Royal Mail's Women of Distinction series in 2008 for piloting the Equal Pay Act through parliament.