I Visited Every Tube Station Hotdog Cart in London and All I Found Was This Lousy Conspiracy Theory

London doesn't really do street food. Yes: we have polished "street food markets"; kebab shops that line the streets like sentinels; and fried chicken places that gratifyingly take up about 30 percent of the city's retail units. But they're all indoors. Controlled. "Clean". There's not that element of risk, of chaos. The idea that you are flirting, constantly, with the prospect of a bowel infection. There is nothing, in this grand old city, that approaches that typically New York experience of having an army of mustachioed men shouting about pretzels and gyros at you from every street corner.

Or at least, there's almost nothing. For London has one thing that no other city does so well: the Tube Station Hotdog Cart Men. The ones who seem to just drift up, either through the pavement or from the ether-like fumes of the sewers, only shifting into existence when you're heading back from the pub, in those magic hours where the normal bus cedes service to the nightbus, when Leicester Square is all but empty. They do not exist in daylight; they do not exist in the wholesome hours of the night. It is only near the witching hour, there, and only there: that's where The Tube Station Hotdog Cart Man thrives.

But what drives The Tube Station Hotdog Cart Men? Who are they? Where do their carts come from? Where are they stored during the daylight hours? Do they just make their sausage prices up on the spot? And what's better: ketchup, mustard, or ketchup and mustard? There was only one way to find out: tour as many Tube Station Hotdog Cart Men hotdog carts in one night as I could, eating meat and getting some answers.

To find a Hotdog Man, you have to think like a Hotdog Man. I become slightly surly, hunch my shoulders a bit and head to consumer heaven: Oxford Circus. At 10PM, tourists would be heading back to their airbnbs and… oh, this isn't a good start. No Hotdog Men to be seen; just a man banging a drum.

There's nothing at Tottenham Court Road either, and Farringdon – dead cert, saw-the-guy-there-with-his-cart-two-days-ago Farringdon – is deserted. This isn't going well. I'm actually hungry. Time to bust out the big guns and head to Camden, spiritual home of "selling all manner of shite on the street to people who should know better".

If I can get a street hotdog anywhere, I will get it here.

There are punks. There are goths. There aren't any hotdogs. There are a surprising number of neon policemen, though, so it's time to ask some awkward questions about renegade meat vendors. A faintly pissed-off looking policeman tells me that hotdog carts operate without licenses, so they're going to get closed down and moved on periodically.

"So, they're illegal?"

"Yeah, illegal."

These aren't just hotdogs we're looking for; they're Criminal Hotdogs. This is bratwurst banditry, and it might explain why we've been hopping from popular place to popular place without a single sausage sighting – the Hotdog Men are fugitives of the law. Or are they? Are they really illegal, or was that just a ruse to deter me from these potentially questionable snacks?

A second group of police are much more evasive about the whole issue: "You'd have to ask the council," they snaffle. "But I wouldn't eat one, mate!"

We stop at a comparatively upmarket and definitely legal hole-in-the-wall place to tide us over, and to provide a control sample to compare the Tube station dogs to while I ask the man behind the counter if there's any needle between street sellers and people with permanent places, like himself. I'm imagining a turf war, shoot-outs where guns and ammunition are replaced with squeezy condiment bottles and streams of ketchup, but he just shrugs at me. "I don't love the competition, but we don't bother each other. People make a living, it's fine."

His hotdog tastes of disappointment. The bun, sensing the mood, falls apart faster than my fastidiously assembled plans for the night, leaving me with yellow-tinted fingers from the atomic mustard. Four tube stations – five once we come up dry in Kentish Town – and no hotdog carts. We retreat to the pub. The problem, we surmise, two drinks deep, is this: it's too early. The Hotdog Men won't show their faces yet, because everyone is too sober to pay £4 for a burnt sausage.

Crestfallen, we head to Angel – the "Baby's First Night Out" London destination du jour, and home to the biggest Tube escalator on the map. We hum to the top of it. On the air, that smell – salty, pricked with fat, onions. There is a Hotdog Cart Man here.

Through mouthfuls of sausage, onion and perfectly aged bun (stale), I get chatting to my hero: the first Real Hotdog Fella I've seen all night. He chats happily, telling me that he's always perched outside Angel in the evening, that this is his patch… but I'm getting a weird vibe from the guy with him. He's just standing there, ignoring the onions. Staring. At me. And when I find out that the Actual Hotdog Fella doesn't know where his cart comes from, just that "some guy in a van" drops it off, my alarms go off. His minder – let's be honest, he's a minder, and I bet he's armed – ducks behind my head to hide from photographer Chris' camera. This is a little unsettling. What's going on here, I think. What's going on, in the world of hotdogs?

Next up is Leicester Square, and there's the same Hotdog Man/ minder combo keeping tourists fed about two minutes from the station – right outside a closed McDonald's. I eat a dog in the warm yellow glow of the place, and feel alive for the first time in eons.

Leicester Square's Hotdog Man has been doing this job for 15 years, carefully rotating sausages with tongs, tending to wilted onions, watering down ketchups… and is utterly in the dark about where his cart comes from, or goes, after he's done with it. It's a man with a van, he says. The same van as the guy in Angel, I ask? He doesn't know. Is… listen. Hear me out, because I know how this sounds. But: is Big Hotdog a thing? Is… is Big Hotdog evil?

We head to Victoria, but BH's tendrils haven't extended there. So we head south to Brixton. Tiredness and sobriety are beginning to hit hard now. Two drunk girls tell me a life hack: that the best way to go up an escalator at night is to sit down on it. We are deep in those magic, musky hours where the hotdog vendors make their bread.

At the top of the escalator, the nicest man in the world is there to hand me a hotdog and kill some time shooting the breeze. No henchman here, just a man and his mysterious, van-delivered cart. Without the constant vigilance of a minder and an array of (I am imagining) lethal weapons to keep him on his toes, the hotdog is a bit plain. The mustard isn't its cart-standard tongue-sizzling here, it's just a bit anaemic and nothing-y. Potential watered down into blandness. Maybe it's just destination-dependent.

Suddenly, the minders all make sense. They aren't there for moral support, or to keep an eye on the onions while the main hotdog guy goes for a piss – they're there to make sure nobody gets too aggro, either a drunk person going at a Hotdog Man or vice versa. They keep the peace, they keep an eye on the fivers and they make sure the Hotdog Cart goes back in the Hotdog Van where it belongs. It is they who are the true arms of Big Hotdog – the man turning the sausage is merely a pawn.

We loop back to locations we toured through earlier, hoping to see hotdogs emerge from them. Oxford Circus remains a disappointment – by day and by night – but Tottenham Court Road is a winner. Armed with a bottle of blue Fanta from an off-license and the memories of a pair of girls complaining of the cold in the shop ("It's like the South Pole in here! It's like the South Pole! I feel like I'm in… Africa or something!"), I'm told by my dog man that "we're all friends here".

I am tired now, and weary. The experience of eating the night's fifth hotdog is difficult to put into words, but… well, think back to the last dinner your nan made for you – your favourite nan, your best nan – only she's getting to the stage where she's starting to forget things, then suddenly she's bustling around the kitchen all bright-eyed, and she's shovelling roasties onto your plate because you're a "growing boy", and they're all crispy on the outside and fluffy in the middle, and in that one single moment you just feel that warm burst of sunshine in your chest like everything's going to be OK.

This hotdog is the exact opposite of that.

One mouthful is just onions and bread, the rest is exactly what you'd expect a fifth sober hotdog of the night to be. I'm staggering a little as I exit Holborn station – no cart there – and wander up to Farringdon for the final stop. It feels right to honour the heroes of the carts, subjugated and beaten down by their shadowy Big Hotdog lords, by eating from as many of them as I can in a single night, but this is actually quite hard work.

There's a big splodge of mustard more or less directly on the groin area of my jeans that I didn't notice before. This night has left me a more undignified man than I was when I woke up this morning.

The lights at Farringdon blur into view. There's no sizzle. No cart. No van. Just a security guard locking up the station gates as I raise my arms in triumph. I've vanquished Big Hotdog. I've taken all they could throw at me, and I've eaten it, grossly undercooked onions and all. I've won.

If there's a lesson here, it's that Big Hotdog absolutely exists, and warrants further investigation before it's too late.

If there's a second lesson, it's probably that eating five decent-sized hotdogs from the side of the street in one night will give you meat sweats for at least 48 hours. One out of ten, would not recommend.

@ThatChris1209

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