At the risk of sounding as miserable as Harry's Uncle Vernon, one of the most magical things about 'The Making of Harry Potter' Warner Bros Studio Tour is the way all your money disappears from your pockets!
The moment you walk through the doors of the vast studios, a pester power spell is cast on your kids and, like a Hogwarts pupil on a broomstick, you're turned upside down and shaken until every penny has flown, Golden Snitch-style, into the company tills.
Aside from the £85 price of a family ticket, there's just so much - too much - stuff to buy. And it's all hugely expensive.
From wands (£25) to school gowns (£75); from polo shirts (£31) to chocolate frogs (£7.50); to a photo of your kids riding on a broomstick (£12) to a mini-movie of your kids riding on a broomstick over the turrets of Hogwarts (£25), every possible variation of Harry Potter merchandise is for sale.
I managed to escape by handing over a relatively meagre £40 for a Harry Potter clapper board, a fluffy owl and a T-shirt for my three children, aged 11, eight and six – until I became bamboozled myself and bought a mug with an owl's eyes on it – for £12.95 – begging the question: who's the real mug?
By the end of the experience, my own pockets were as baggy as Wizard Dumbledore's sleeve!
But that makes me a weak parent: nobody makes you buy this stuff. And if you have what it takes to resist the power of the pester, the Harry Potter Studio Tour was not only a fantastic day out – it was a sanity-saver at the end of the way-too-long school summer holidays.
I have to confess, I've never read a Harry Potter book, nor seen any of the eight blockbuster movies filmed at the vast site at Leavesden, near Watford.
But my 11-year-old stepdaughter is a Potter devotee and her younger brothers are experts at wand-waving, as the state of my bathroom floor testifies.
The youngest, in particular, is obsessed with owls, having amassed a collection of 20 fluffy ones over the course of his six years on the planet, so the chance to immerse himself in an experience where owls are paramount was, hmmm, a hoot!
The start of the tour is very organised, deliberately guided to give everyone context about what they're about to experience.
Groups of around 100 visitors are first taken into a holding room, where an enthusiastic Potter evangelist explains the phenomenal success of the franchise, which started with Harry Potter and The Philosopher's Stone in 200, and that we're about to find out how all the films were made at the Studios.
We're then led into a movie theatre where a virtual Danielle Radcliffe and his co-stars introduce a whistle-stop, action-packed, head-spinning trailer of all the Harry Potter films rolled into one. And then the real fun begins.
As Daniel departs the cinematic stage, he invited us guests to follow. Cue curtain rise and suddenly we're in the The Great Hall of Hogwarts, setting of many a feast and the occasional duel.
From here, we're free to wander at our own leisure, exploring The Great Hall, moving through to The Big Room, exploring The Back Lot, marvelling at Creature Effects, strolling down Diagon Alley, before arriving at the gobsmacking spectacle of The Model Room, where a gigantic model of Hogwarts Castle that took 40 days to make hogs centre stage. The only stage, in fact!
None of this does the four hours we spent on the Tour justice. My kids explored with wide-eyed wonder, their mouths agape, as they tried to take in the surreal scene.
They took part in a wand-waving masterclass, rode a broomstick and flew through mysterious streets and snowy landscapes, drank Butter Beer (quite disgusting: tastes like American Cream Soda), climbed aboard the Knight Bus, walked across Hogwarts Bridge, strolled through Gryffindor, Dumbledore's Office and Hagrid's Hut, and came face-to-face with a myriad of strange creatures, from Dobby to Aragog to Buckbeak and Voldemort.
And they learned secrets – lots and lots of secrets – about how the astonishing special effects in the Harry Potter films were achieved.
Want to know how Harry's Invisibility cloak worked? Or how candles were made to float? How did the team make Hagrid (played by Robbie Coltrane) so much bigger than the other characters? Or a frying pan that washed itself? How did the Hungarian Horntail shoot fire from its mouth? And how did the film-makers create those incredible scenes in the wizarding sport of Quidditch?
I could tell you, of course, but I'd disappear in a puff of smoke if I did!
• For details about The Making of Harry Potter Warner Brothers Studio Tour go to http://www.wbstudiotour.co.uk/
• Thank you to Littlewoods for inviting us along. http://www.littlewoods.com/