The executive director of Greenpeace International and former Rhodes scholar tells Alicia Clegg what he took away from Oxford – and relates some of his experiences since.

Why did you apply to Oxford?
To be honest, I didn't know much about Oxford. I was 21 years old and standing trial for violating the state of emergency [in South Africa, 1986]. Some progressive professors at home encouraged me to apply for a Rhodes Scholarship, really to get me out of the country. On the day I heard I had been successful, my home was raided. For the next four months, until I fled to Oxford, I was basically on the run.

What were your first impressions?
It was a big culture shock. The night I arrived, I slept for 12 hours and was woken by a knock on the door. When you are on the run, you become very sensitive to knocks on doors. But here was a lady offering me breakfast. And I remember it had snowed overnight.

What did you study?
I started doing an MLitt on the resistance movement in South Africa and finally – it took for ever – converted it into a DPhil.

Why did it take so long?
When Nelson Mandela was released, I went home. I got caught up in the elections and discontinued my studies for about five years. I didn't submit my thesis until June 1999.

Why did you go back to it?
I had a sense of responsibility. I was told I was the first black activist to be awarded a Rhodes Scholarship. In fact, I think there was a big doubt over whether to give it to me, given my unconventional background. I didn't want my example to count against other activist students who might apply in the future. And I don't like to not finish things that I've started.

Did you enjoy Oxford?
It wasn't the most enjoyable time. It was a very repressive period in South Africa and my family and friends paid the price. My younger brother was imprisoned and my best friend was murdered. You feel guilt because you aren't there. But friends in Oxford were warm, generous and supportive.

How did you spend your time at Oxford?
My journey to Greenpeace through non-governmental organisations [NGOs] really began at Oxford. I spent a lot of time with Oxfam. Before I came to Britain, I had never heard of Oxfam or Greenpeace. Through the University, I was involved in setting up Rhodes Scholars Against Apartheid. I was also quite active in the Oxford Coalition Against Apartheid.

You went on a hunger strike?
I did seven days on just water to raise money for South African kids living in exile. The times when I could do things connected to home were probably the times I felt most at peace. I was contributing in some small way, even if from a distance.

What did you take away from Oxford?
The nature of the apartheid system and those who organised against it meant that in South Africa I generally interacted with people who had the same world view as I had. At Oxford, I had to learn how to engage with people who had different perspectives. A lot of my work since has been as a bridge-builder, pushing people to focus on the large number of things they agree upon and to disagree respectfully on the smaller number they don't. The other things I took away were some really strong friendships, through which my time at Oxford lives on, and my degree.

Has your degree been useful?
For many people I come into contact with, people who are struggling and living in poverty, a DPhil from Oxford doesn't hold any meaning. But, there are some parts of my work – trying to influence heads of state and international bodies such as the UN – where it does help that I have a DPhil.

What role would you like Oxford to play in climate-change politics?
Obviously Oxford has things it can contribute to climate science. I do think, more generally, Oxford graduates are an important body of opinion-makers. Ultimately, every professor and student has an interest in securing the future of the planet.