Richard Humphreys spent a good part of five years, between the ages of 18 and 23, living inside a nuclear submarine, which he describes variously as ‘sleek, black and athletic looking’, and ‘this fierce black messenger of death’, and ‘this huge, black leviathan’, and ‘a killing machine’, and ‘silent as death’. The first time he sets foot on it, he tells us, ‘I was shitting it.’ This is not the last we will hear of his negative emotions, or the state of his bowels.

We are in the latter part of the Cold War. Humphreys is a sailor. The submarine is HMS Resolution, part of the Polaris fleet. It is 425ft long, 33ft wide and 30ft from top to bottom. Humphreys describes it as ‘cigar-shaped’. From the outside it looks huge; from the inside it feels tiny. It carries nuclear missiles that are, we are told, more powerful than all the bombs dropped in the second world war put together. But Resolution is not just a bombing machine; it’s also a hiding machine. Nobody knows where it is — including almost everybody on it. You’re under the sea, within firing range of Moscow. That’s it. It does your head in.

Lots of things about living on a nuclear submarine do your head in. The payload; the fact that you’re carrying the payload; the fact that you don’t really want to fire the payload; the fact that you might; the fact that, if you did, most of the people you love might already be dead. Also, the other submariners: their proximity; the relationships that develop between them when they have to live together in a steel tube under the sea for ten weeks at a time. Plus: the farts, the smell, the masturbation of others; the bullying; the lack of sunlight and vitamin D; the whittling away of privacy to a tiny nub. The fact that you will ask yourself: what am I doing down here?

The nuclear missiles. Humphreys tells us about them early on, meaning that they are always on your mind. There are 16 Polaris missiles on the submarine, ‘each with a staggering nuclear yield of about 225 KT (kilotons)’. He puts this in context: the bomb dropped on Hiroshima had a yield of, at most, 18 KT. So Humphreys’s submarine has the capacity to destroy at least 200 Hiroshimas. He describes Resolution as having three sections: the front, for eating and sleeping; the middle — ‘armageddon’; and the back, which is for ‘propulsion’.

I can’t cover the entire theme of defecation that runs through the book, but I can give you a sense of it. Resolution itself moves through the water like a sea creature; it expels waste matter (‘gash’) using a ‘gash gun’. Sometimes the sewage tank gets blocked, and must be unblocked with compressed air. But you can’t expel this air into the sea, because you’re supposed to be hiding, and air bubbles might give the game away. So the air must be absorbed back into the submarine, like a flatulent whale trying to hold in a ton of gas: ‘Think of something like a giant collective fart mixed with oil, body odour, rotten food, fags and booze and you’re getting my drift.’

Also, life in a submarine plays havoc with people’s body clocks, leading to constipation and diarrhoea. And sometimes the lavatories won’t flush, ‘which meant you were defecating on to someone else’s shit’. That, let me just say, is when it starts to get really disgusting. (There’s a bit about threadworms.) In any case, submarines can be gross.

But what an absorbing read! There’s a bit about the Queen Mother visiting the submarine base at Faslane, and a bit when Margaret Thatcher climbs aboard, and disappears, and someone says: ‘You’re blocking the hatch, you big cock splash!’

For Richard Humphreys, the best part was the first taste of fresh air when  Resolution came to the surface: ‘Here I was, standing up top, drinking huge gulps of fresh air down into my lungs… It was the best feeling in the world.’