Nearly 50 years ago, in 1972, a phone call alerted me to a demonstration at the Covent Garden opera house in London. Would I write it up in the paper? It was a matinee and a throng of starry-eyed teenagers were waiting at the stage door for the dancer Margot Fonteyn.

As she appeared, and to general dismay, banners shot up, urging Don’t Dance to the Apartheid Tune. The Hain family – Adelaine and Walter, and a couple of their children – were telling the much-loved prima ballerina how unwise it would be to do Sleeping Beauty before segregated audiences in Cape Town.

Fonteyn went anyway, but the Hains, who had been forced out of South Africa when life became impossible for them, had made another inroad in the British consciousness. Two years earlier, their son Peter had spearheaded a direct action campaign against the touring Springbok rugby team that led to the exclusion of South Africa from world sport.

Back in Pretoria, resisting the apartheid regime had been a different matter. It was there that Adelaine Hain, who has died aged 92, cut her political teeth. She was born into a conventional family. Her father, Gerald Stocks, ran a building firm in Port Alfred, in the eastern Cape, while her mother, Edith (nee Duffy), a Christian Scientist, raised their seven children. After school at Victoria girls high in Grahamstown, she worked on her local newspaper.

Moving to Pretoria, to a job in a building society, she met and in 1948 married Walter Hain, who had by then resumed his architectural studies after second world war service in Italy. When he qualified, they moved to Kenya, to the UK for two years, and then to several towns in South Africa before returning to Pretoria, nerve centre of Afrikaner nationalism. The years away had radicalised them.

Facebook Twitter Pinterest Adelaine Hain in Pretoria, South Africa, in 1963

They joined the diminutive Liberal party, which was hated even more than the blacks-only African National Congress (ANC) because of its non-racial membership. Soon the Hains were running the Pretoria branch. The presence of Africans, Asians and “coloureds” at party meetings in their home caused disquiet in the white suburb of Hatfield. On one occasion Pretoria University students stood at the fence shouting obscenities, threatening to come in and restore apartheid order.

Meanwhile Adelaine patrolled the courts and police stations looking for missing men whose wives had been given short shrift by the Special Branch, and sent food to the families of these political prisoners.

With the shooting of 69 unarmed protesters at Sharpeville in March 1960, a key event in the liberation struggle, South Africa moved swiftly into police state mode. The Hains’ phone was tapped, their mail intercepted, the house placed under Special Branch surveillance. One night Peter and his brother Tom woke to find security policemen rifling through their clothes drawers.

When Adelaine and Walter were caught red-handed putting up posters in support of an ANC stay-at-home strike, Adelaine chewed through the draft of an incriminating discussion paper and spat out the shreds. They were released after 12 days for lack of evidence.

More publicly, when Nelson Mandela stood trial for leaving South Africa illegally, a pint-sized figure sat alone in the white benches. Each day Mandela greeted her with a clenched fist, to which Adelaine replied in kind, while offering her trademark cheeky smile. When a magistrate wrote ordering her to desist from “subversive activity”, she asked for chapter and verse, but was told only she would know. A newspaper cartoon had the police minister telling his security chief to “Find Adelaine Hain, check what she’s doing and tell her she mustn’t.”

Soon enough she, and a year later Walter, were banned under the Suppression of Communism Act. This severely limited their freedom of movement and communication, though they were granted special permission to speak to each other. Adelaine was undeterred, helping a political escapee to cross the border and sending hidden messages to Liberals in Pretoria prison.

Facebook Twitter Pinterest Adelaine Hain, right, with her son, Peter Hain, on the Free Mandela protest outside South Africa House, London, in 1986

The showdown came with the trial of their friend and Liberal colleague John Harris, who in 1964 had planted a bomb at Johannesburg railway station that killed a woman. For the 18 months of his detention and trial, Harris’s wife and baby son lived with the Hains. They disapproved of what he had done but knew it was their duty to look after his family. This was perhaps the finest thing they ever did. After Harris was hanged, neither Adelaine nor Walter was allowed to attend the funeral. It was left to 15-year-old Peter to deliver the address.

Their lives were in real danger. The justice minister, John Vorster, bellowed menacingly that Harris had been recruited to the bombing campaign “at the house of Hain”. Liberals were being put under house arrest, stripped of their civil rights; a home was burned out. Architectural firms were told, no government contracts if they employed Walter Hain. In 1966 the Hains emigrated, looking for a safer life in the UK. If they thought their struggle was at an end, they were mistaken.

They set up home in Putney, south-west London. Adelaine had four teenage children to settle in, but found time to become involved with the burgeoning Anti-Apartheid Movement. In time she did her shift on the picket outside the South African high commission in Trafalgar Square – where, much later, she would celebrate her 80th birthday.

They were a sports mad family, which led Peter, aged 19, to launch the Stop the Seventy Tour Committee, running on to rugby fields as the white Springboks scrummed down. Adelaine became its campaign secretary.

It was like old times again. Now the British Special Branch tapped their phone. And there was the day Adelaine came into the dining room to find a letter bomb on the table, courtesy of agents of the South African security services, waiting to explode. When, in 1991, Peter was elected Labour MP for Neath, Adelaine became his part-time secretary. Their one big disagreement was over Peter’s vote in favour of the 2003 invasion of Iraq by the Blair government, of which he was by then a member. The elder Hains were firmly against.

When Walter and Adelaine returned to a free South Africa, where some nervous siblings had once cut her out of their lives, the next generation were proud to welcome her. They recognised that their aunt had simply, but then again with great difficulty, done the right thing.

She is survived by her children, Peter, Tom, Jo-anne and Sally, 11 grandchildren, 21 great-grandchildren and two great-great grandchildren. Walter died in 2016.

• Adelaine Florence Hain, political activist, born 16 February 1927; died 8 September 2019