When police in visored helmets and swinging batons, ran on to the field at Hamilton's Rugby Park, something came unstuck in New Zealand's self-image as an open, tolerant society.
Anti-apartheid protester John Minto says it felt "alien".
"It was clear we had crossed some sort of line ...
"Police were no longer a neutral party, they were determined to see the tour proceed - conflict was inevitable."
The protesters, led by Hart (Halt All Racist Tours), thought the tour would be cancelled following massive demonstrations around the country and international pressure.
But the Government refused to call it off. Some critics accused Prime Minister Rob Muldoon of making a calculated decision ahead of the general election to back the 1981 tour and curry favour in marginal rural seats, where pro-tour feeling was strongest.
The Springboks arrived on July 19, 1981, and for the next 56 dramatic days, New Zealand headlined news bulletins around the world.
In scenes reminiscent of South Africa itself, protesters clashed with police and enraged rugby fans; rugby grounds resembled war zones, barbwired and barricaded.
During the final test match at Eden Park, Auckland, a low-flying light plane disrupted the match by dropping flour-bombs on the pitch. (Pilot Marx Jones served six months' jail for the stunt.)
Public confidence in the police was battered when riot police were filmed beating unarmed "clowns" and bare-headed protesters at a sit-down.
The repercussions were even felt within Robben Island Prison, where future South African president Nelson Mandela and other prominent African National Congress (ANC) leaders were imprisoned.
Mandela was quoted as saying that "the sun shone through the dark corridors of the cells" when he heard about the protests in New Zealand.
When the tour wasn't called off after the Hamilton fiasco, Minto says the protesters realised it was going to be a "hard slog".
They had already resolved to go further than just banner-waving if necessary.
"We believed it was such a serious affront to human rights, we were prepared to take civil disobedience action to try to stop it."
Minto says that although the protesters lost the battle to halt the tour, they "won the war".
Not only did the protests show black South Africans that New Zealanders felt solidarity with their struggle, but it dealt a serious psychological blow to white South Africans.
"As a result of the protests here, no other major rugby-playing country would accept the Springboks until apartheid was gone. We closed down South African rugby for 10 years."
Then Auckland Rugby Union chairman Ron Don, who was also a member of the NZRFU Council, says he "wouldn't change a thing".
"Like almost every rugby person, I was pro-tour and nothing that has happened since has altered my opinions," he says.
"I think I speak for all sports in New Zealand, when I say we didn't then and we don't now inquire into the politics of any nation we were playing against, either home or away."
Don denies there was much division within rugby circles at the time, despite the fact that then-All Black captain Graham Mourie stood down, with veteran centre Bruce Robertson.
Prominent former All Blacks, including Ken Gray, Bob Burgess, Mick O'Callaghan, Chris Laidlaw, John Graham, Bevan Holmes and 1960 captain Wilson Whineray, plus coaches, administrators and referees also spoke out against the tour.
Don says they were "never criticised or attacked in any way".
Mourie, who is now on the board of the NZRFU, says from a personal point of view, he is sad he never got to play the Springboks - but he has no regrets about his stand.
"I felt that playing would have given tacit support to the unjust regime in South Africa - it would have been hypocritical of me to say apartheid was wrong but go ahead and play just because I wanted to."
In the aftermath of the tour, Muldoon clung to power in the general election by one seat. In 1985 the NZRFU proposed an All Black tour of South Africa but plans were halted by the High Court after two lawyers successfully argued it would breach the union's own constitution.
An unofficial tour by "the Cavaliers" went ahead in 1986 but the All Blacks did not officially tour South Africa until after the fall of apartheid.