Although it is tempting to think that the idea of hiding underground in response to environmental and social cataclysmic forces is squarely in the ballpark of those who take the Book of Revelation a touch too literally, it is also the subject of rigorous academic analysis. But before you let that put you off, it needs to be said that the author of ‘Bunkers: Building for the End Times’ (Allen Lane, £20, ISBN  9780241336014), is about as far away from the clichéd caricature of the ivory-tower-ensconced professor as you could possibly get.

Bradley Garrett is an urban explorer and ‘experimental geographer’ who, you feel, has finessed his academic career into propelling himself around the world in order to visit some of the strangest subterranean buildings known (and often unknown) and make them known to the wider public. In the process he’s put himself in personal danger, endured a variety of weird experiences, ended up with a criminal record and written a book.

Humans, as Garrett tells us, have been bunker-aware since prehistory. And while he’s interested in the physical entities themselves, he’s also caught in the headlights of the bunker as an expression of our deepest fears, from pandemics to climate change, nuclear war to unpleasant people wanting our stuff.

But there’s much more to ‘Bunkers’ than simply explaining how, why and where we hide, whether it be in the natural cave formations of ancient Turkey, or by following California’s tech billionaires to their fashionable safe havens in New Zealand. Garrett explores the global movement of preparation (‘prepping’) for the end of the world and makes a hugely persuasive case that ‘survivalism’ is slowly becoming more mainstream.

Of the Covid-19 pandemic, he comments: “As the virus spread, supply lines, international travel and trade routes, economic systems and social norms collapsed in a matter of weeks. The pandemic was precisely the kind of breakdown preppers had prepared for. While most people panic-bought toilet paper, the preppers closed their blast doors.”

What makes Garrett’s book fascinating is his portrayal of the balance between fringe thinking and the real world. On the one hand, we get to know the self-important prepper entrepreneur whose paranoid daydreams seldom get further than the drawing board, while on the other we are given credible accounts of substantial projects designed to sustain post-apocalyptic communities in secure underground environments.

All of which exposes the fundamental tension that will consume readers of this highly addictive book: that of wanting to dismiss the world of bunkers as the province of the ‘green ink brigade’ while acknowledging that there has never been a more compelling case for taking emergency preparation seriously.

You can’t fault Garrett’s work ethic either, as there are numerous last-minute revisions punctuating the text that bring the Covid-19 pandemic, alleged Russian hacking and Donald Trump’s often unfathomable relationship with the media (both social and otherwise) into focus. Superb stuff.