When Gordon Brown was 23, as a post-graduate student and Rector of Edinburgh University, he was an active and vocal opponent of apartheid in South Africa. His opposition to apartheid then reflects the progressive values that he now takes into this election campaign.

When David Cameron was 23 he went on a free trip to South Africa, funded by a lobbying group founded by a former member of the South African military intelligence to bust sanctions against South Africa, and organised by a member of the Monday Club. This doesn’t suggest that as a Thatcherite researcher in the Conservative Research Department in 1989 David Cameron was a supporter of apartheid, although some of his party’s MPs at the time were. Nor does it suggest that he agreed with his then-party leader Margaret Thatcher that Nelson Mandela was ‘a terrorist.’ Nor does it even suggest that Cameron supported his party’s opposition to sanctions against the apartheid government (although there is no evidence that he didn’t.) But it does suggest poor judgement, and at best ambivalence towards the situation in South Africa in the late 80s.

I was reminded last week of the struggle against apartheid by spending a day in Soweto, and by visiting the memorial to Hector Pieterson, killed by the police aged 13 in 1976, and the Apartheid Museum in Johannesburg. South Africa, in the grip of world cup fever, seemed to be a nation on the rise. Everywhere were construction projects, with new road and rail systems being built. A lively democratic politics exists everywhere. A new generation of ‘BornFrees’ (young people born after the end of apartheid) are ready to take over. In Soweto, people were cutting their front lawns and washing their cars. Slowly, the terrible poverty, disease and unemployment is being tackled, although violent crime is on the rise.

When Cameron visited South Africa, apartheid was in its final, most vicious phase. The facts of the massacres of school children in the Soweto Uprising in ‘76 were well known in Great Britain, where many of the ANC-in-exile were living. By the 1980s, the states of emergency imposed by the Botha regime were on the news as a regular feature, with the scenes of armoured Caspir trucks and police with dogs and rubber bullets on the streets of the townships. The campaigning of the Anti-Apartheid Movement was at its height, especially in the university system that Cameron had so recently left. You couldn’t move for Nelson Mandela bars; the Special AKA’s Free Nelson Mandela was on the radio and in student discos. In the Apartheid Museum there’s a huge photo of a UK Anti-Apartheid demo in the mid-80s, with young people with their placards, doc martens and flat tops.

Apartheid was a defining issue for the politically-active in the 1970s and 1980s.

A charitable interpretation of David Cameron’s actions in 1989 might be that it was simply a free holiday: some time in the sun drinking Stellenbosch served by people whose government thought were racially inferior. But at 23 people are responsible for their actions in way that they are not at, say, 18. And if they were then employed by the party that they now lead, it was not a personal matter, but a political act. It was an arrogant two-fingered salute to all of us in the anti-apartheid movement in the 1980s. And it provided succour to a regime founded on racism, at the very time the regime was struggling for its life against the bravery of the people of South Africa and their supporters around the world.

In 1989, millions of decent people in the UK stood shoulder to shoulder with the majority population in South Africa by backing the international boycott of goods and services: people from the churches, trade unions, and across the political spectrum, including a few Tories.

David Cameron was not one of them.