As she acknowledges in her autobiography, she could never have done this half as effectively as she did without Beck.

Suzman forced the government to take her seriously because her slashing attacks on their policies were always based on hard facts. Beck was the one who ensured that she had them at her fingertips. When Suzman went sailing into battle against the likes of Hendrik Verwoerd and John Vorster she often had to hope like hell that Beck had done her homework properly and that the facts she'd fed her were accurate. They always were.

Local and international parliamentary correspondents relied heavily on her political nous too, often coming to her to be briefed on what Suzman's response to particular Bills would be and why.

Beck's extremely dry sense of humour was an added attraction.

Beck and Suzman were a formidable combination, and a large part of the reason was the chemistry between them. They called each other "dear". And no matter how desperate Suzman's "dear" sounded - her requests were often extremely urgent - Beck's response, emanating from a cloud of cigarette smoke, was invariably an unflustered "Yes dear, what can I do for you?"

Suzman recalls: "I don't remember the two of us ever shouting at each other. That for me is pretty good, I can tell you."

They were both political animals with a shared commitment to liberal values, and intellectual equals. They'd both been university lecturers: Beck in social sciences at the University of Cape Town, Suzman in economic history at Wits.

Beck (née De Villiers) was born into an Afrikaans family in the Free State town of Ficksburg on May 22 1916. Her mother, "a battle-axe" according to Beck, was the mayoress of the town when it first got electricity. Her father was an attorney.

After Ficksburg Primary School Beck attended Wynberg Girls High and then UCT. She did a BA.LLB there and, just before World War Two, became the second female advocate in South Africa to be called to the Bar. She did not, however, practise.

After her law degree she studied philosophy. She was a member of the UCT Students' Representative Council, for a period its only female member.

She was voted head woman student by her fellow students, one of whom remembers her as small, very popular, quite good-looking and very intellectual.

Beck was an impressive debater, winning the university debating society's best speaker award a couple of times.

In 1941 she joined the Women's Auxiliary Air Force. She was seconded to Internal Security and compiled top-secret reports on individuals believed to be involved with the Nazi-sympathising Ossewabrandwag and the Broederbond.

After the war she lectured at UCT, then joined the United Party as its chief research officer. In 1953 she stood for Parliament in the staunch National Party constituency of Vasco. She was addressing an election meeting in Epping when the hall was invaded by a band of Nat thugs and she had to jump out of a window to escape a beating.

This didn't stop her from trying again in 1958, but again she lost. In the interim she became a member of the provincial council for South Peninsula.

At the UP conference in Bloemfontein in 1959 she was among the small band of UP members who decided to break away and form the Progressive Party.

In the late 1950s she married Hastings Beck, a former Rhodes scholar.

Beck retired from her research post in 1974 when Suzman was at last joined in Parliament by six fellow Prog MPs.

In 1981 Beck stood in Simonstown as the Progressive Federal Party's candidate for the provincial council, but lost.

After her husband died she moved to an old age home in Fish Hoek and waited somewhat impatiently for her end. Intellectually astute as ever, she complained that there was no one at the home she could talk to about things that interested her, and that she was bored stiff.

Beck is survived by three nephews and a stepdaughter.