Harry Potter and the Philosopher’s Stone (2001) was released almost 15 years ago. That means the film is now older than half of the Hogwarts students we came to know and love. Let that sink in for a moment.

To celebrate, Warner Bros. Studio Tour London perused their archives and found some fantastic props from Harry’s first adventure. Their ‘Finding the Philosopher’s Stone’ feature is full of wonderful remembrances and insights into the story’s adaptation onto the silver screen.

Romancing the stone

Now, you’ll no doubt recall that there are few places in the wizarding world better safeguarded than Hogwarts. But the protections placed on the immortality-granting Philosopher’s Stone were enough to make a Gringotts vault look as accessible as a municipal swimming pool.

I noticed on show several of the crucial conundrums that kept the stone out of reach. Like the harp Professor Quirrell enchanted to lull Fluffy off to sleep. It was rather calming to hear the lilting strains of John Williams’ score, at my fingertips (I do so love a good ‘press the button’ opportunity).

Devil’s Snare was jiggling at passers-by – its treacle-like tentacles entwining ready to grab as I walked briskly past – and visitors dodged moving pawns from Professor McGonagall’s chess set.

I didn’t see my heart’s desire this time in the Mirror of Erised, the last obstacle for anyone in pursuit of the famous stone. Tarnished with age and framed with ornate gilt, it keeps the Fat Lady’s portrait company outside the Gryffindor common room.

Troll bogies: menace or mediator?

Obviously my next task was to learn about troll bogies. I couldn’t possibly share the exact ingredients, but it made me remember fondly the moment Harry got his wand lodged up a troll’s nose. Who knew bogies could bring three young magical people together?

I took a closer look at a reflective surface covered in oil and glycerine, which was used for unicorn blood onscreen. It makes you want to put your hand in swirl it all around, but there is definitely no touching allowed.

I made up for it by whisking a cauldron full of Fluffy’s drool (a bit like egg whites, but less fluffy). I may have got a little too carried away, actually.

The hazards of prop-making

There might only have been one stone in the Harry Potter stories but movie-making is an intense process and accidents will happen. As Tiffany Kearsley, a member of the art department across all eight Potter films, explained to me, getting the right Philosopher’s Stone was more an unusual case of happenstance.

‘These were the original stones,’ she said gesturing to a clutch of examples, ‘but we discovered that they just didn’t look that exciting onscreen. We had a piece of red quartz lying around, so we moulded it and that was that! It’s never normally so simple.’

There is also a hidden stone for visitors to find, but I couldn’t possibly spoil that for you.

Tiffany showed me the intricate work that went into making Neville’s Remembrall – the very same that got Harry his place in the Quidditch team. Each tiny prop might have had a nano-second of actual screen time but the effort that goes into each piece is astounding.

Hagrid’s flute, the flying keys, Harry’s very first pair of glasses – these delicate props could take days or weeks to craft by hand. I asked Tiffany how often props wound up broken.

‘Things got broken a lot,' she confided. ‘The kids were bored a lot on set so you’d see them tapping their wands. Daniel Radcliffe must have got through at least 90. He used to use them as drumsticks on his legs.’

With the arrival of the eighth Harry Potter story, Harry Potter and the Cursed Child Parts One and Two, one area of the Studio Tour has taken on new meaning. Most emotional perhaps is the photo composite of Harry’s first glimpse of the Hogwarts Express, followed by a shot of grown-up Harry speaking to his son Albus on platform nine and three-quarters.

A middle-aged Harry might currently be onstage in London’s West End, but the spirit of the 11-year-old one is alive and well in Leavesden.

Finding the Philosopher’s Stone runs at Warner Bros. Studio Tour London until 5 September.