King's Cross is a pother of platform anomalies. As if the existence of platform 0 wasn't baffling enough, another of the station's platforms never existed in the first place. Despite this, it attracts a queue of dozens throughout the day.
Like the Harry Potter books, Platform 9 ¾ started off inconspicuously enough. It was a sawn-off luggage trolley stuck into the station brickwork. You'd have thought only nutty Potter fans would have sought it out. Of course, all Potter fans are nutty enough about the boy wizard to seek it out.
As if by magic, the trolley began vanishing then reappearing around the station. Such was the gravity of the situation, in 2011, Network Rail felt the need to weigh in:
At its new and sorry looking location in a small alcove outside the station on York Way, it looked like the magic of the Potter platform was fizzling out. In fact, the Potter marketeers had something big up their sleeves.
In 2012, the trolley reappeared on the station's new concourse; it had gained some trunks and a cage. Sometimes there was an owl in the cage. Next to it was a new Harry Potter shop called — what else —Platform 9 ¾. That's when the real queues began.
"I told him that our trip would be unfulfilled if we did not stop here," says Stephanie, motioning to her partner. The couple have travelled from Washington DC, and one of them looks considerably more animated than the other.
"I started reading Harry Potter when I was 12 and I'm almost 30 now," Stephanie says, "so it's really important for me to be here where it actually takes place."
For many, this is where the Harry Potter saga all began. You can tell these people they should be visiting the Roman London Wall — not some bit of Victorian brickwork next to a mini Waitrose — but pouring cold water on their excitement is pointless.
"Wingardium Leviosa!" grins 20-year-old Yu-Ji Hyeop, "You know? You know?" He arrived from Korea yesterday with his friend Park dae Hyun, and Platform 9 ¾ figured high up on the list, alongside the Eye and Big Ben.
"And I love Hermione," adds Yu-Ji Hyeop, grinning more.
When Arnaldo, here from Brazil with his friends, found out last year that there was an actual Platform 9 ¾, he knew he had to come. "I really like the whole lore and history of the houses, how everything came up," he says, "maybe the thing about a wand and how it chooses a wizard — that's pretty cool. The characters are amazing as well.
"Now we have to take a picture.... 'Everyone look at me holding a wand on Platform 9 ¾!'"
This won't be the group's only Potter-centric adventure; they'll do a Harry Potter tour while they're in town. Paul and Annie, on a school trip from Lille in France, are visiting the Warner Bros. Studio Tour in Watford this afternoon — their entire day dedicated to a fictional character. What do they love about Harry Potter so much? "I don't know," says Paul, "that's magic, the atmosphere, the characters."
In theory Platform 9 ¾ costs nothing, but it can wind up being more than a trip to the London Eye or Madame Tussauds. Muggles — scarf flapping in the breeze, with the help of a shop assistant — can take their own photos, but a professional snap is £9.50. The rest of the merch is an eye-watering money spinner; the well choreographed shop — owl cages festooning the ceiling, wands stacked neatly on an Ollivanders shelf — is a Harry Potter fan's dream... and probably a parent's worst nightmare.
It's not predominantly kids who are struck with "IwantIwantIwant" fever though. Just like M&M's World, the clientele here consists largely of full-grown fanatics, and they're eager to take something of the Pottersphere home with them: a Hogwarts Oyster card holder (£1.95) a small bag of Jelly Slugs (£4), Harry Potter glasses (£5.99), a chess set (£59.95) or a sterling silver Dobby necklace (£110).
A wand — which, alas, does not pick you — costs in the region of £30. Some of these prices have been conjured from thin air. Next to them, occupying a small corner at the back of the shop, are the Harry Potter books. Surely they should form the centrepiece? But then, who here doesn't own the canon already.
"I'm going to buy a lot of things," smiles Stephanie.
"I think I'll buy something. I don't know what," says Paul.
And Arnaldo? "Yeah probably, some merchandise, I'm not sure what. Maybe just a scarf, something like that."
The shop can't give out quotes — a shame because apart from finding out what the biggest seller is here, we'd like to know if staff must pass any kind of Hogwarts-esque exam. Still, we're impressed to overhear from behind the till a deep conversation about Dumbledore's love life. Maybe chat about last night's match is forbidden, lest the magic be trampled upon.
Platform 9 ¾ perhaps encapsulates London's tourist attractions as a whole — half of them free, half careering towards the astronomical. A lot of the stuff in here (what Alan Sugar might call 'toot') is a rip-off. But like the Royal family, the brand has become an indelible — if divisive — part of London.
Meanwhile, we wait patiently for another bespectacled hero of King's Cross to be suitably honoured. It'll be a fine day indeed when the neighbouring plaque quoting Philip Larkin's Whitsun Weddings is swarmed with bald wig/horn-rimmed glasses-wearing nuts.
And we would pay good money for a keyring from the They Fuck You Up, Your Mum and Dad shop.