Born: July 27, 1930;

Died: April 12, 2021.

SHIRLEY Williams, Baroness Williams of Crosby, who has died aged 90, was a liberal politician who was right at the heart of the profound ideological shifts in the political parties that began in the 1970s and arguably have still not been resolved today.

As one of the original ‘Gang of Four’ – the others were William Rodgers, David Owen and Roy Jenkins – she co-founded a new party, the Social Democratic Party (SDP), which for a brief moment looked like it might change the mould in the 1980s. It didn’t, but Williams remained a hugely influential and popular figure for many decades to come, unfussy and easy-going but robust and radical.

She was also consistent through turbulent times, which probably explains the relative position of the Labour party to her own beliefs. In the 1980s, she left Labour under Michael Foot because she said it was too left-wing, but in the 2000s, she criticised Labour under Tony Blair for being too right-wing and favourable to the free market.

She would have said it was the party that changed, not her, and certainly, she was guided by principles of social democracy that were founded in her radical childhood and remained intact with her for the rest of her life.

The radical principles came direct from her parents. Born Shirley Vivien Teresa Brittain Williams, her father, Sir George Catlin, was a political scientist and an unsuccessful Labour candidate, who would wheel Shirley to Labour meetings in a pram. Her mother was Vera Brittain, the prominent feminist and the celebrated author of Testament of Youth, the famous lyrical protest against the futility of the First World War.

It was a privileged childhood, with two live-in servants, but it was not necessarily easy. Vera was totally committed to her work and Shirley knew not to disturb her – “she was completely uninterruptible before 5pm unless there was a major fire,” Williams once said.

When the war broke out, the young Shirley was then evacuated to Minnesota and was separated from her parents from the age of nine to 13. On her return, she was sent to a boarding school in London, which she hated.

Her radicalism was already emerging though. She joined the Labour party at 16 – the earliest age you could do so – and became the Labour agent of Chelsea. She also worked a number of jobs, including land girl, and chambermaid, and while working as a waitress in Northumberland when she was 17, organised a strike and won higher wages for the staff.

She then won a scholarship to Oxford, where her interest in politics continued, and she became the first woman chairman of the University Labour Club. After university, having married fellow student Bernard Williams in 1955 – they had a daughter Becky – she worked for a brief time in journalism, on the Daily Mirror, before throwing herself into politics.

She stood twice for Labour in by-elections, in 1954 and 55, and then again in 1959 before eventually entering Parliament as MP for Hitchin in 1964. She was one of only 29 female MPs at the time and remembers going into the Ladies’ Room at the Commons to discover comfy sofas and an ironing board.

She was swiftly promoted to the lower ranks of government, although opinion was divided about her prospects. Some predicted that she could be the first female Prime Minister, but others thought at the time that her dishevelled and slightly disorganised appearance might work against her. Lady Astor, the first woman MP, is said to have told her: “You will never get anywhere in politics with hair like that.”

She began to make her mark, though. In 1966, as junior minister at the Ministry of Labour, she had to take over from Ray Gunter, the Secretary of State, when he fell ill, and dealt with the aftermath of the seamen’s strike. She is also remembered for her period as Education Secretary when she was responsible for the continuing implementation of comprehensive schools. She also served on Labour’s ruling National Executive Committee between 1970 and 1981

However, disillusionment with the party was setting in. Troubled by the leftward lurch of the movement she had belonged to pretty much her whole life, she quit to help form what was dreamed of as the all-conquering party of the centre ground. She felt she had no choice, but it meant she came to be reviled by the party’s left who denounced her as a traitor.

For a while, the prospects for the SDP looked very promising indeed. In 1981 Williams fought and won a by-election at Crosby to become the SDP’s first elected MP and the party was riding high in the polls. But after the Falklands War, Margaret Thatcher’s popularity recovered and Williams lost her seat in 1983.

The SDP project then collapsed amid recriminations and was subsumed into the Liberal Party which, through a series of name changes, finally became the Liberal Democrats.

Williams’ first marriage having collapsed, in the late 1980s she married Professor Richard Neustadt, a distinguished US academic and former adviser to Presidents Kennedy and Carter, and took up the post of Professor of Elective Politics in the John F Kennedy school of Government at Harvard University.

She became a life peeress in 1993 and sat in the House of Lords as a Liberal Democrat and continued to remain deeply immersed in the political scene. She said of herself that she had been “stuck with the same values for the last 50 years” but it was this consistency, delivered in a manner free of fuss or pomposity, that helped make her so popular.

In the autumn of 2004, she retired as the Liberal Democrat leader in the House of Lords and in her farewell speech to her party conference held out hope that the traditional divides of politics might yet change. “The mould may not yet be broken,” she said, “but the crack is dramatically widening.”

Baroness Williams is survived by her daughter Rebecca.