When the four-minute nuclear warning sounds - if the new world of random terror affords us such a luxury - John Emin can both run and hide. For the inventor and businessman has a nuclear shelter in his cellar.
While the nuclear device that has just exploded in London creates a deadly wind lashing radioactive fallout across the Home Counties, Emin will be cosy in his concrete pile beneath the ground, waiting for it to settle before going upstairs to farm cockroaches, or whatever opportunity presents itself in post-catastrophe East Grinstead.
Yes, Emin's 22-year-old shelter is enjoying a new sense of relevance. "Everyone I know is talking about dirty nuclear bombs, al-Qa'ida, chemical weapons, biological weapons," he says. "I always thought there was a fair chance of nuclear conflict. Now we have these madmen who want to kill off democracy." He built the shelter in 1982, during the Cold War, and by 1990 it appeared to be redundant. Now, it's being taken seriously again. Yet, as he is trying to sell the property, bunker and all, these renewed fears of attack must bring him mixed feelings. "People are telling me, 'You don't need the money. Why sell it now?'"
The journey to Emin's nuclear-resistant home takes one through the kind of high-value Home Counties countryside where large houses lurk behind hedges - the kind of prosperous normality rendered sinister by acquaintance with British apocalypse dramas such as Quatermass, The Day of the Triffids and Survivors. Eventually, a gravel drive gives way to a small group of houses, once part of the estate of an adjacent manor house that is now a conference centre.
This is Emin's patch, where he has lived for 27 years and bought up three children with his wife Barbara. They want to move: it's too high-maintenance, as it consists of three different houses in shared grounds, one of which his daughter's family live in. Emin says the estate cannot be split up, which may be why it has only had three serious viewers in the six months since it has been on the market. It's pegged at £1.5m, but Emin wants to fetch more because of the value the shelter represents.
In John and Barbara's self-built house - under which is the nuclear shelter - we sit on a white leather suite, drinking tea and eating chocolate bourbons as Simply Red play in the background. Barbara shows me the latest addition to the house: a spa block with Turkish bath and a hot tub. It seems appalling that this Hello! scenario could be blown sky-high by some zealot with a hold-all full of Kazakhastani plutonium.
Naturally, we discuss doomy "what if" scenarios. Emin says we'd be better off with a conventional nuclear bomb, rather than a uranium-in-the-suitcase job. "If a dirty bomb goes off in London, I don't know how they'd clear it up. In other words, it's better to have a conventional strike. With a dirty bomb, you could be talking about a quarter of a million years." That's an awful lot of tinned peas to get in from the local Spar.
John Emin is Tracey Emin's half-brother. "My dad is a Turkish Cypriot, and I'm one of his official children, if you like. He had a few hotels in Margate and... let's just say that he had another family." John mother, who has died, "was an old-fashioned mum who stood by her man" and they grew up in Shooter's Hill, south-east London, where John and his two sons now run the family drainage business. Barbara shows a framed copy of Tracey's self-portrait, Every Part of Me's Bleeding, with the artist in the bath. "I love Tracey, she's a lovely girl," says John. "It's not her fault what happened with dad, and we're all very proud of her." She just happens to be from the non-nuclear side of the family.
On route to the shelter, John directs me to a corner of the room, where a hefty door leads onto concrete steps. The atmosphere chills as one walks down through another hefty door, into a decontamination chamber, and then into a large, 22ft by 20ft, living room - perhaps that should be the "surviving" room. "In the Eighties, we felt that nukes might fly at some point, and people said you couldn't survive a nuclear war. I wanted to put another view, to show that you could survive as long as you had a good shelter." Oddly, he has never done a nuclear drill with his family, and has looked into the possibility of turning it into a recording studio.
It's an oppressive space, with thick, grey walls, marginally cosier than a John Pawson pad. "It's a concrete box," says Emin, who has made a few concessions to homeliness: red tiles in the entrance lobby; brown and beige tiles in the decontamination chamber. In the living room there's an Ikea-style pine kitchenette (no, he does not have stockpiles of canned food) and a pine ceiling and insulation to stop condensation.
There are bits of enigmatic machinery around, of course: two generators in an ante-room, and a big air filter in the corner of the living room that can process the nasty radioactive, chemical or biological dust.
The filter sucks in air through the ground, although he doesn't want to pour light on this magic, nor does Emin wish to discuss the two escape hatches: small doors that make your average bank safe look like flatpack. "I don't want to talk about these features," he says. "That's valuable security information." Then there's a room for bunks, a shower and two toilets. The shelter can hold up to 76 people.
Emin does not seem to be a crazed survivalist, so why build the bunker? "When Margaret Thatcher was in power, she said that all local councils should build bunkers," says Emin, who saw a business opportunity and built his own show-bunker. "It's a 'three atmosphere' shelter," he says, "designed for a one-megaton bomb. It'll survive a five-megaton airburst, but not a ground burst." It's easy to get lost in nuclear jargon, and Emin can certainly talk the talk.
Now to the nuclear nitty-gritty. It cost about a quarter of a million pounds - a lot of money in the early 1980s - and it doesn't sound as though the business ever flew. "I sold two drawings," he says. "I'm not very satisfied at the business side. Inventors are like this. When I see a problem, I try to solve it." The end of the Cold War was bad news for nuclear shelter builders, but maybe they're on an upturn now.
If the bomb goes off, I venture, I'd like to be close to the blast. "People keep saying this," says Emin, clearly tired of such defeatism. "I'm a pragmatist. If a bomb goes off, do your best to survive." The shelter is his testament to the life force.
OK. How long would you have to stay down here? "It depends on the fall-out phase," says Emin. "The real nastiness is in the first two weeks. Then, you could have the situation where you shouldn't come to the surface after three months. After then, you'd have to find out about the footprint [how far the fallout has spread]." Only then would you gingerly step outside with Geiger counter to hand.
Fascinating stuff, but not exactly a mainstream purchase, and at the moment, the question is not "when", it's "if". "It'll take a special type of buyer," he admits. "It needs someone with the money and the need." A paranoid rock star or freakish cult, perhaps? "We were joking that it could be the Beckhams," says Emin. "They've got everything, but not total security. All those big guys around them aren't going to help them from chemical and biological attacks." As for Emin, he doesn't want a nuclear shelter in his next place, he wants a Turkish bath. "Then al-Qa'ida would start something with smallpox. That'd be just my luck."
Emin's property is being sold by Lane Fox of East Grinstead, 01342 326326. The guide price is £1.5m