During Nelson Mandela’s 1962 trial in Pretoria, before he was sent to Robben Island, Winnie turned up each day, often magnificent in traditional chiefdom dress.

My anti-apartheid activist mother Adelaine was often alone, showing solidarity, in the whites-only section of the public gallery. Once, when my younger sisters went with her, dressed in their primary school uniforms, Winnie bent down and kissed them, to the very evident horror and disgust of the onlooking white policemen, who spat and cursed. The very notion of a black woman behaving that way towards two blonde girls offended every apartheid instinct. But Winnie didn’t care.

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She was indomitably defiant. Later, suffering so much and bringing up her own two girls while Nelson Mandela served his 27 years in prison, she was beaten up, banned, then banished to remote Brandfort in the Orange Free State, harassed and imprisoned too.

Once, when relatives turned up unexpectedly in Brandfort, she was convicted of contravening her banning order. This, among many other things, restricted her to meeting only one person at a time. Fearless in the face of the apartheid police state, she became the increasingly iconic representative of Nelson Mandela.

She also tutored him. Winnie was among the first to understand the significance when, in 1976, black children were gunned down while protesting against apartheid schooling in Soweto, outside Johannesburg. Soweto exploded, triggering fresh resistance and repression in other black townships throughout the country.

Tragic, heroic and ultimately deeply flawed, Winnie can be correctly criticised for her rogue later life

Visiting Mandela on Robben Island, she urged him to identify with and support this new wave of unrest, even when it took the form of a wave of “black consciousness” that veterans in his African National Congress saw as offensive to their non-racialism.

It was nothing of the kind. Mandela listened to Winnie, and embraced the young activists, who soon began joining him on the Island, rebellious and suspicious of his old guard.

The two had fallen in love after Nelson, two decades older, had spotted the vivacious, charismatic young social worker waiting for a bus as he drove past.

But as she later observed, she never had the conventional marriage she hoped for. She had married a freedom fighter, not a husband. Soon he was on trial, then released, then driven underground when they would occasionally meet illicitly; he hardly knew his two daughters when he was sent to prison.

Facebook Twitter Pinterest Nelson and Winnie Mandela in their wedding day Photograph: AFP/Getty

Security services made it as difficult as possible for her to visit, preventing her from travelling by train, forcing her to fly or drive the 800 miles. Mandela’s letters to her displayed a touching affection and deep admiration. Throughout, she was steadfast in his support. But she became increasingly wayward, taking younger lovers into her new Soweto home. In the 1980s she became embroiled in the murky murder of young activist Stompie Moeketsie, for which she was later tried and found guilty, the judge labelling her “a liar”.

Nelson, after his release, spoke of being the “loneliest man” after their divorce. But he never shunned her. She had become a quasi-revolutionary to Mandela’s reformism in the transition from apartheid to non-racial democracy, presaging a debate live today, especially among younger elements in South Africa.

Tragic, heroic and ultimately deeply flawed, Winnie can be correctly criticised for her rogue later life, but her courage and radical spirit in adversity should never be forgotten.

• Peter Hain is a former Labour MP and minister for Africa. His biography, Mandela: His Essential Life, will be published by Rowman & Littlefield in July