"Your first nappy is free," says Joe. "After that, they're a quid each. There are two rooms with changing tables for customers' use. And a playroom for cuddles."
It's Saturday night at the Adult Baby Club, a monthly party held in a basement round the back of London's King's Cross station, where, despite the council's best efforts, there's still quite a seedy vibe. According to ABC's website, tonight's event is a "safe place for ABs [adult babies], DLs [diaper lovers], their daddies, mummies and friends to play".
Joe guides me through the gloom into the main room, where a group of blokes stand around chatting and drinking bottled beer to soft rock. It's a pretty normal scene, like staff drinks at an IT firm, except everyone's wearing disposable nappies.
Joe's been helping out at the party for seven years.
"I do the spanking night on a Thursday as well," he says. He shakes my hand. He's small with East End cabbie glasses, but he has a ferocious grip, no doubt honed by all that paddling.
Speaking of which, in the corner of the room, beneath an intimidating-looking crucifix (which presumably gets more of a work-out at the venue's other parties), there's a paddling pool on the floor filled up with coloured plastic balls. Two guys lay in it, chucking them at one another. One wears a romper suit and the other, in his fifties, has grey, mad-professor hair, a blue gingham dress, white socks and Mary Jane-style shoes. Above them are lampshades with pictures of aeroplanes on them. Around the room are teddy bears, boards with animal stickers, rubber play mats and a toy box containing plastic Fisher Price-style games.
Adult babies have hit the news recently, with the new "adult nursery" Nursery Thymes – run by Derek and Maxine Ventham – featured on Mail Online and The Jeremy Kyle Show as a result of locals in Bootle, Liverpool kicking up a fuss about this unconventional new business. The Venthams moved there from Portsmouth to escape abuse from neighbours. Some people wrongly assume that adult baby fetishism is connected to paedophilia. In fact, paraphilic infantilism, also known as autonepiophilia, is the desire to return to an infant-like state, and infantilists are not attracted to children.
"As soon as you mention adult babies, they say, 'You're a paedophile.' But it couldn't be further from the truth. We don't want to be with children, we want to be the child. This is my relaxant. Half an hour in a nappy and my stress is gone," Derek was quoted as saying in the Liverpool Echo.
This is certainly borne out at the club, which is strictly for over-18s, where grown men are "playing", chucking balls, chasing one another around and whooping to pop music, including, appropriately, Baby Spice's "Maybe".
"I'm not into the sex side as much as the playful side," says Simon, a tall, skinny coding guy from Croydon.
So when did he get into wearing nappies?
"When I was a kid. I like the dressing up. And the feeling of wetting yourself."
A guy in both a diaper and a leather dog mask takes a running jump at the paddling pool and lands on his stomach with his feet in the air, before joining in the fun with the balls. I wonder whether, in assimilating two fetishes in one outfit, he's being greedy?
"There's a lot of crossover between ABs and other scenes," Simon says. "Some of us are furries. He's into pet play."
It all sounds quite complicated.
"It is. There are plenty of divisions, even among the groups. Furries can be into it because they like the art, because they enjoy the feeling of being encased in fabric, or because they like wild sex parties."
What is striking about tonight's event is the lack of sex. We're in a dank gay dive bar, where, judging by the hooks in the ceiling, some pretty heavy meat-grinding takes place on a regular basis. For a fetish event, things are pretty tame. Perhaps that has to do with the clientele. Rather than the ball gags and medical restraints you might expect here on other nights, it looks more like a Games Workshop meet-up, full of skinny white boys with doughy muscles, potbellies, fluffy goatee beards and straggly ponytails.
Standing by the bar, where "Breast Milk: £1" has been added to the shots menu beneath the tequila and Jägerbombs, I watch dog mask guy suck water from a bowl through a straw. I then get chatting to Kevin, a programmer from Greenwich in a Hobbit T-shirt with the loud, confident voice of someone who's skilled in devising highly technical algorithms and doesn't care who knows it. I ask him why so many of the men here are nerds.
"If you're young, intelligent and socially awkward, then there's a good chance you'll end up in IT," he says. "And generally people who are into kink are more intelligent. Then there's the whole Freudian thing that we were isolated as kids and so we recreate that isolation through niche interests as adults."
Presumably, out of all the hobbies you could have, being an adult baby is one of the most isolating?
"I live with a vanilla housemate. When you're a total pervert, people tend not to mention it. Except when they're drunk. Then they might ask why you make a crinkling sound when you sit down for breakfast in the morning. Or why you have a massive pile of nappies in your room."
Simon hovers into view.
"Are you going to try a diaper on?" he asks.
To be honest, I'm feeling a little out of place in my jeans and shirt. I look round, taking in two guys in nappies sitting on the toy box daubing a colouring book with green and yellow crayons. The only other person in normal clothes here is a creepy Brazilian man in a leather jacket who looks a bit like Tony Montana and who's spent the night freaking out a crowd that must be pretty immune to weirdness.
"I'm tired," I say. "I'll probably go soon."
"You don't need much energy to have a nappy put on," says Simon.
His logic is unassailable. But, call me a square, the idea of wearing one – let alone having someone else put it on for me – just isn't all that appealing, so I make my excuses. My stance is not shaken later when, pushing back the curtain of one of the "changing rooms", I see dog mask guy lying bollock-naked, his legs held above his torso by one man while another sponges his arse with a wet wipe.
Thank god there's a strict no "booty-cake" rule in operation here.
"I love putting on a nappy, going down the supermarket and shitting myself in front of everyone."
By 10.30PM, the party (which only runs until 11PM) is winding down. I talk to the guy in the Gingham dress, who introduces himself as Kiki. He tells me he's straight, although most of the guys here are gay or bi. I should check out an event down in the country near Farnham, where apparently several women attend.
Where did you get the dress?
"BHS basic school range," he says. "I have it in three colours."
Thus far, the people I have met have dispelled any prior suspicion that adult babies are simply a bunch of oddball pervs. As odd as a preoccupation with wearing polymer polypropylene against your adult genitals may be, the guys here have been pleasant and, for the most part, normal-acting, if you don't look below the waist. But Roy, a red-faced, 45-year-old sparky up for the night from Southampton, is a little more forthcoming about his leisure time tastes. He fixes me with intense eyes and enthusiastically describes exactly what it is he's into.
"There's no bigger turn-on than shitting yourself in public," he says. "I love putting on a nappy, going down the supermarket and shitting myself in front of everyone."
Any particular aisle?
"It's the humiliation I like. I reckon most people are into it, if they're honest. Shitting themselves. Me and my wife used to wear nappies together. She liked it, too, 'til we split up.
"There's loads of people into it. I go cruising with a wet nappy on. There's always at least one guy who thinks it's really hot. I'm coming back down here later for the after-party. Last time I wore a soaking nappy and got in an orgy with ten guys."
"You only live once. If you want to shit yourself, you should be free to."
Presumably he's disappointed by the strict no hot-bombs rule in operation here?
"Well, it's a bit silly, isn't it? You only live once. If you want to shit yourself you should be free to."
Fortunately, Tony Montana moves in on the conversation. I wish Roy luck for later, giving him a wave in lieu of a handshake, and then leg it out into the cold King's Cross night, where the only changing I plan on doing is from the Piccadilly to the Central line on the way home. Adult Baby Club hasn't made me want to break out the Pampers any time soon, but for the guys who frequent it, it's certainly a much more welcoming place to do it than in the Morrisons veg aisle.