A Glasgow couple who campaigned against Apartheid have revealed the chilling threats they faced at home and abroad – and spoken for the first time about their family sheltering former South African leader Nelson Mandela before he was imprisoned for 27 years.

Radha Chetty, 80, fled the country for Glasgow in the 1950s and later married teacher Maggie. The pair were prominent anti-racism activists in the 1970s and ‘80s, which made them a target for the authorities, and shadowy figures who followed them around and photographed them.

Meanwhile, in South Africa, Radha’s family are believed to have given refuge to Mandela at a remote farm when he was on the run. The discovery was made by Radha and Maggie’s daughter Dhivya, 40, when she was making a documentary about their struggle.

Radha is from Pietermaritzburg. His father owned a music shop, which is now ‘Joe’s Liquor Store’. His family farm is gone, replaced by industrial buildings. All that remains is a pecan tree, planted by his father. His family were forced to move because the land was declared a “white area” by the government.

Radha said: “So many people lost businesses, lost livelihoods, and it is precisely for that reason that my parents said: ‘no, this is not a country for you. If you want an opportunity, get an education. And the only way we can give you an education is to send you abroad’.”

On the three-week journey by ship to the UK, Apartheid was enforced, meaning “non-whites were segregated,” Radha said.

When he arrived in Glasgow, he said his first instinct was to sit at the back of a bus. “In South Africa the space reserved for people of colour was upstairs, six rows at the back,” he said.

He was so conditioned by Apartheid, he was concerned he would be unable to communicate at university without being shouted down. “Apartheid tried to contain your activities, your thoughts, your belief in yourself,” he said.

“Schools were segregated, where you lived to a large extent was segregated. Just generally, life was all compartmentalised. Although we were so-called citizens of South Africa, travelling between provinces was restricted. We as Asians had to get a permit…in all aspects of your life, the state controlled everything.”

In the documentary Radha was overcome with emotion when he talked about the realisation that he could speak his mind at the University of Glasgow, where he studied engineering. “Suddenly I realised that I could voice my opinion,” he said.

Radha met Maggie in Glasgow and the couple were married in 1977, later having two daughters. Radha had left behind the overt racism of Apartheid South Africa, but the couple still faced prejudice in Glasgow.

Maggie said: “Racism expresses itself in all sorts of subtle ways. If Radha and I were standing together in a shop, people would assume we were not together. People told racist jokes all the time.”

Radha said they were even insulted “from time to time” but he now feels comfortable about putting his arm around Maggie in public because “things have changed”.

The couple were involved in the anti-racist movement, and Maggie was assaulted by police officers who waded in to a demonstration against the National Front in Glasgow in 1976. The moment was photographed and appeared in a newspaper at the time.

Maggie said: “I got kicked very hard between my legs and my arm was thrust up my back. I was dragged along and there was a collective gasp from the crowd. When we got to the police van this brutal big police officer lifted me up and threw me in, and I landed on my face. There was a chap in there already who had his nose smashed across his face.”

Radha and Maggie were also involved in the anti-Apartheid movement in Scotland and said they were often watched and photographed by shadowy figures in the street, and received sinister phone calls.

Maggie said: “Once I was in my flat in Partick and I got a threatening phone call – a big, rough male voice – which said something like we’re coming to get you. I phoned Radha and said I’m scared.”

Radha left his flat to come to Maggie’s aid and after he left two men arrived at Radha’s door. His cousin was in the flat and “two big burly guys” tried to push their way in, according to Radha.

Maggie said: “They were terrifying. You knew you were dealing with people who would stop at nothing to maintain South Africa’s relationship with the United Kingdom.”

He and Maggie are convinced their phones were tapped during that period. Maggie said she could hear voices on the line. Radha remembers workmen coming to his door to fix a fault on the line. Radha had not reported a fault and turned them away.

in 1981 they visited South Africa with Dhivya. It was then illegal for couples of different ethnic backgrounds to marry. Maggie said: “Everywhere we went we got stared at. Among the Indian and African community the stares were curious. But when we were in the centre of Pietermaritzburg in the white areas people turned around in the street and muttered things about you. It was because you were (considered) a traitor to the white race.”

Despite the threats in South Africa and at home in Glasgow, the couple continued campaigning against Apartheid, because they knew the movement was gathering momentum. In the early 1980s Glasgow’s Lord Provost gave Nelson Mandela, who was then in prison, the freedom of the city. The local authority also renamed the street where the South African consulate was based, Nelson Mandela Place.

“We knew we were making headway,” said Maggie. “And that gave us such confidence. We had to get rid of this thing which was so appalling, for our young children, for their future.”

The couple’s daughter, Dhivya Kate Chetty, who made the documentary, said: “In a strange way, Apartheid created my family. Without it Radha would never have met my mum Maggie. I’d heard fragments of their story and family tales of resistance against apartheid, but I hadn’t fully pieced them together.”

During the course of her research for the documentary, Dhivya discovered that Nelson Mandela may have been in hiding at the Chetty family farm, shortly before he was caught and imprisoned.

A friend of Radha’s late father revealed that the Chetty family offered food and shelter to the former South African leader when he was on the run.

Mr Ismael Jnr, who appeared in the documentary said: “Mandela was in hiding at the Chetty farm and from there he proceeded towards northern Natal, and he got caught on the way, or he was arrested on the way.”

“I didn’t know. I’m delighted,” said Radha, in the documentary.

Speaking to the Herald on Sunday, Radha admitted he doesn’t know for sure if it happened. However, a family photo which was recently rediscovered shows his brother, Vasu, standing behind Mandela after he was freed. Vasu, a GP, treated those who resisted Apartheid.

Radha said: “There was social contact by some members of the family with Mandela…the one thing I can say with a degree of certainty is that the family helped people that were escaping police. There was a home in a remote place surrounded by fields which had a secret wall, which made it quite safe.”

Dhivya said: “To find out years later that my family may have had a closer involvement with Mandela than we all realised was amazing. I guess we’ll never know for sure, but finding my uncle in a picture beside him may be the closest we’ll come to any proof.”

Dhivya made the documentary to chart the history of Scotland’s struggle against apartheid. She said: “I was taught from a young age about the inhumanity and injustice of apartheid and I took part in some of the anti-apartheid campaigning in Glasgow so it felt important to explore that. The film is also a tribute to Glasgow, its people and of course it’s a Glasgow love story.

Maggie said: “I’m so please she did it because it’s really important to know your history. Any progress we have is because people fought for it. We’re just one little story from millions of stories in the Apartheid struggle, but it’s everybody’s story. And it’s Glasgow’s story, and that’s what we’re very proud of.”

Radha recently regained his citizenship of South Africa after sixty years in the UK and forty years as a British citizen.

In the documentary, Radha and Maggie return to South Africa for a family wedding. Radha said: “I’m more relaxed today being in this country than ever before because I feel South African, just being here.

“Mandela said it’s time for reconciliation. To harbour that hate of people is wrong. But to harbour a hate for a system that oppresses and deprives others of opportunities in life, that I still hate and will always hate because it’s unjust.”

Glasgow, Love and Apartheid is on BBC Two Scotland on Tuesday.