Like thousands of other South African activists forced into exile in the depths of apartheid, Isaiah Stein, who has died in the UK at the age of 79, was all but forgotten in his homeland after democracy dawned.

But Stein's contribution to the struggle against apartheid, particularly in the battlefield of sport, was considerable. After fleeing South Africa in 1968, he spent the remainder of his life in the UK, where he helped entrench the sports boycott and provided support for many exiles and fellow activists.

Stein was born to a coloured family in Durban in 1931, the son of a pastor and property developer. After both his parents died during his teens, he moved to District Six in 1948. There he became an amateur boxer, using the whimsical moniker "Boston Tababy", and was arrested for the first time for the crime of fighting a white opponent.

He also worked for and befriended a Jewish family in Cape Town, the Steins, who in due course adopted him. Stein took their surname, perhaps as a way of evading the authorities as his political activism began in earnest. Stein also got into property development, and during the late '50s, met his first wife, Lillian Jacobs.

Stein was radicalised by the Sharpeville Massacre in 1960, and soon he was a famously energetic chief organiser of the Coloured People's Congress, allied to the ANC. The authorities increasingly rated him as a real threat, and in 1964 both he and Lillian were dragged naked from their house and tortured. He carried torture scars on his legs for the rest of his life.

Only a 14-day hunger strike by Stein forced Lillian's release, and he was later the first to be put under 24-hour house arrest. Four years later, with Nelson Mandela jailed and the future looking grim, Stein fled on a ship with his family to Southampton, where the Bishop of Stepney, Trevor Huddlestone, welcomed him and found the family lodgings.

Soon after settling down in London, Stein began working as a distribution manager for leading African literature publishers Heinemann.

But the outlet for his political energy was the South African Non-Racial Olympic Committee, and he was a famously fiery participant in demonstrations against South African touring teams to England.

He and Lillian inculcated a spirit of hard work and service in their children, who became accustomed to sleeping on the floor whenever various visiting struggle activists were allocated their beds. The couple later divorced, though remained close, and he married a Capetonian, Deborah Julius.

When freedom came to South Africa, Stein was deeply moved and made several trips home, to vote and testify about his torture and imprisonment to the Truth and Reconciliation Commission.

He did not return for good, though, and expressed the misgivings commonly felt by exiles who felt excluded from and disappointed by the post-apartheid reality. Stein once claimed that if he wrote an autobiography, it would be titled "All for Nothing."

Stein had 10 children. Three of his eight sons - Mark, Brian and Ed - became professional footballers in England. Mark earned one England cap, and starred for Chelsea in the early '90s.