I finished school actually at Easter, in my third year of sixth form, because I'd already taken A levels twice. I didn't see any point… I got my scholarship to come to Cambridge, I saw no point in staying on and taking it a third time. So I left at Easter and decided to get my National Service out the way before I came up. There was a kind of slightly, I suppose, a bit of idealism in it. I was a young chap… I thought actually I should do my National Service and not try to get out of it, and actually I wanted at an earlier stage even to be one of the Bevin Boys, you know, the people who went down the mines. There was alternative National Service, which was during the war… I even sort of contemplated that, but somehow… but somehow I think that it either stopped by that stage or was no longer an option. So I deliberately chose to do that, and many of my contemporaries didn't. I mean they decided to go up straight away and by doing that many of them actually avoided National Service altogether because three years down the road, if you stayed on and did research, you know, you didn't have to do it.

So… but, my time in the Army was not I would say tremendously productive. I mean I went into REME, which is Royal Electrical Mechanical Engineers, but they didn't use my mathematics at all. I could have been trained in radar or whatever it was, like a lot of my contemporaries. I tried to get into the educational department. So I ended up as a clerk at headquarters in REME, which was an uncomfortable, sort of, job. I used to cycle home at weekends; it was not very far from where I lived. But I think what you got out of it was some exposure to a cross-section of life that you don't meet in the academic world, which I think is a helpful part of, sort of, forming your character. So I think that was beneficial in that sense.

I had spare time, and I corresponded with my contemporaries who'd gone to Cambridge and they would tell me what they were doing and I’d sort of spend my spare time thinking a bit. I remember thinking about higher dimensional polyhedra, you know, trying to classify higher dimensional polyhedra, regular solids, on my own. I remember getting as far as discovering there was a difference between odd and even dimensions. I think I was mainly in four dimensions, and I discovered there was in fact four dimensions because there was no Euler's formula – that you could work out the sort of ratios of various sides, but you couldn't determine the absolute values easily […] memory… and I think I have some notes somewhere. So I played around with various little problems to keep myself mathematically alert, and so they sent me problems that were being set in Cambridge, the kind of clever questions that they throw at students in the first year and I tried my hand at that. But that wasn't very time consuming. I read some books. I remember reading Hardy and Wright, you know, Introduction to Number Theory [sic], a very good book to read. And articles in Encyclopaedia Britannica. So I did a bit of background reading on the side. And I think the main benefit of being in the Army was that… when I came out the Army actually a little bit early.  I did just less than two years because it was possible, although I'd left in April, for [the] Army for reasons which I can explain, didn't actually call me up till October, because the reason was that my father wasn't a British national. You see he's… complicated… he was actually a technically stateless person. So when I left, asked to be called up, they didn't call me up, and I wrote and asked, ‘Why aren't you calling me up?’ They wrote back and said, ‘Well you've got dual nationality. You were born in this country, but your father isn't British, so you've got to wait until you're 21 to decide which nationality you want to have’. Well then I explained to them that actually my father didn't have a nationality, he was stateless, so it was a choice between British nationality and nothing. So it was no choice… so really, couldn't I be called at up at 18 instead? Well, very reluctantly the War Office accepted this logic and finally they agreed and then they sent me a notice summoning me to appear at Carlisle within 24 hours or be court-martialled, or something like that.

So that anyway, I went in, in October and so… but instead of staying two years till the following October, I got out early to come up for the long vacation term in Cambridge beforehand which you could do. There was a kind of… scientists particularly did lab work in the long vacation term… mathematicians didn't have anything to do but they could come up and spend six weeks studying. So my tutor, being [an] enlightened chap, wrote to the War Office and said, you know, ‘It was very important that he should be allowed to come up and do his study beforehand’, and it worked, so I got out early and I came up.

And I remember very clearly the sort of transition from being in the Army, and then coming to university instantaneously, a tremendous sense of you know, liberation. So I think what I gained from it was coming back to the university with enormous enthusiasm to study. Whereas those who'd gone straight from school to university, some of them I think had a bit of, sort of… were a bit exhausted. They'd studied, worked hard, passed exams and they came up here and carried straight on, and some of them lost their sort of enthusiasm. And I came up here having been in the Army two years and went into the Trinity College library and it was marvellous. So I was full of enthusiasm, and I think probably, might have said I’d wasted time, but in retrospect the effect on your psychology is so important that probably it might even have been beneficial. And I didn't find that… there's a danger that sometimes people think you get rusty, you know, you lose the… but I don't think that really worked. You brain at that age is still pretty active and so I think the two years were not productive in any very obvious sense, but they had some side effects which probably were not bad and you were exposed to a bit of rough and tumble in the Army, and probably toughened your physique a bit. I remember winning some cross country race when I was in the Army – running in battle-dress through many miles of countryside. And I know that the irony was, at the end of this I went to see the commanding officer who congratulated me and gave me the prize which was a packet of cigarettes. I've spent most of my life since arguing against tobacco.