WATCH with glittering eyes the whole world around you because the greatest secrets are always hidden in the most unlikely places. Those who don’t believe in magic will never find it…

So said the late Roald Dahl, whose fantasy novels have bewitched children with sales of more than 300 million. It’s a fantastic figure, yet only half the 600 million Harry Potter books that have been bought in 85 languages.

Whatever your take on JK Rowling’s controversial views on gender, she certainly knew how to bring magic to life on the printed page, and then in the eight box office blockbuster movies that followed.

And that magic is recreated in all its enchantment on the Warner Bros Studio Tour London: The Making Of Harry Potter at the Leavesden studio complex near Watford.

I’ve just returned from a three-generation visit – me and my wife, our grown-up kids and their children, aged 10 and 12 – and can confirm that we’re all still suitably spellbound.

That Roald Dahl quote at the head of the post is particularly apposite because the Studio Tour of sets used in the movies, shot on the very same spot, delivers up secrets and surprises around every corner, and in every nook and cranny.

It’s suggested that the average duration of the self-guided tour is three and a half hours. We were there for more than four, and could easily have lingered longer. If we’d broken for lunch in one of the many eateries, it could easily have been five hours or more.

I’d last visited shortly after the tour opened for business back in 2012, and it was impressive then, but over the years the attraction has grown, adding further sets, props and more photo opps than you can shake a selfie stick at.

So what should you expect?

You’re greeted upon arrival by an outdoor boulevard of giant wands, and some of the giant chess pieces from the original Philosopher’s Stone outing that sparked the film frenzy.

Once inside – there are bag checks and airport-style security arches to pass through – a large open-plan foyer and food hall offers chance to relax before your timed ticket tour starts, but be warned there be dragons. Well, one dragon, but it is huge.

The first 20 minutes of the tour is a pre-show, starting in a room full of talking portraits of cast, crew and fans, then moving through into a cinema where a short film narrated largely by Daniel Radcliffe, Emma Watson and Rupert Grint, offers an introduction.

A spellbinding special effect, which I won’t spoil by detailing here, ushers you in to Hogwarts’ hallowed Great Hall, currently set out for students to take their OWLS exams under the watchful eye of dastardly Dolores Umbridge.

As part of the current ‘Magical Mischief’ season, there are pyrotechnics, smoke and flashing lights to recreate the scene in which the older Weasley twins wreak havoc to disrupt Dolores’ draconian Ministry of Magic regime.

From here on in, the tour is self-guided – digital audioguides are available for hire but, in any case, myriad video screens feature crew members explaining how they worked their magic.

During the season, watch out, too, for occasional pop-up live demonstrations. While we were there, we saw the Invisibility Cloak at work, the flood of letters through the Dursleys’ front door, and how we were made to believe a cape could fly.

There may well have been more but there’s so much to see and do here that you won’t see everything, not even if you decide to book an early tour and stay the whole day.

A cleverly winding path makes the most of available space to take you on a journey through thousands of props and intricately detailed sets initially including the Gryffindor Boys Dormitory and Common Room, the Slytherin Common Room, and – an early favourite – Albus Dumbledore’s Office.

Look out for the Pensieve, from which memories could be revisited, the Sword of Gryffindor – so important in the film franchise endgame – and the Telescope, one of the most expensive props made but only ever seen in the background.

Dumbledore’s robes are on display here, too. Indeed, there are costumes drawn from all the movies throughout the tour, together with wigs and tiny finishing touches. See if you can spot Marvolo Gaunt’s ring, revealed to be one of Voldemort’s horcruxes.

The Potions classroom, domain of first Severus Snape and later Horace Slughorn, is next up, with shelves of mysterious bottles and jars, a self-stirring cauldron and the Half-Blood Prince’s perilous potion textbook among many in evidence.

At this point on the tour, there’s a diversion to green screen booths, where visitors can pose for stills and videos astride brooms or in ‘Wanted Wizard’ posters. You’ll learn how Quidditch scenes were filmed, and also how to empty your wallet.

Be warned that photo packages start from £20, £40 and £50 depending which you choose, and although the head says ‘No’, the heart – and a spot of pester power – will inevitably change that to a reluctant sigh of ‘Oh, go on then…”

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There are, however, several free special photo opps along the way, too. You can make a broomstick rise from the ground ready for flying lessons, use a wand in spelling lessons and be made Hagrid-huge by the clever use of distorted mirrors.

From here, you’ll pass Hagrid’s flying motorcycle, and one of the Gringotts Bank vault carts, with a fascinating video showing how digital effects and physical props were seamlessly blended to create some of the most iconic Potter scenes.

Up next, in quick succession, are Hagrid’s hut, the Ministry of Magic, with its green tiled walls and sculpture, and a creepy corner devoted to The Dark Arts, including a life-sized recreation of the infamous torture scene in Malfoy Manor.

It’s a reminder that, for all those sugary sweet moments, Harry and his pals are fighting for their lives against He Who Must Not Be Named – Oh, hi Lord Voldemort! – and his minions. The props here are all so suitably sinister.

It’s an appropriate foreboding of the Forbidden Forest area through which you must pass next. It’s dark, suitably spooky and home, of course, to centaurs, an animatronic Buckbeak, and giant spiders that hang from webs above smoking, bubbling pools.

(If you’re not an ardent arachnids admirer, then rest assured that there’s an alternative path through the forest which by-passes the spiders. They’re not really so scary but I can imagine that they’d unsettle youngsters who worry about such things).

Throughout our visit, we’ve been on a quest of our own, by the way. A free ‘passport’ included in the cost of each ticket encourages visitors to collect embossed stamps along the way, search for Golden Snitches and Pixies, and answer questions.

It’s fun for the young and young at heart alike, makes you examine your surroundings carefully, and will have you hunting high and low (there’s a clue in there when you get to the toughest Snitch of them all, hidden in Gringotts Bank Hall!).

That’s the first half of the tour. To read about Platform 9¾, studio Backlot sets including Privet Drive and Professor Sprout’s Greenhouse, a gold rush and a terrifying day at Gringotts, and the Hogwarts model to beat them all, click here.

For full details of the Warner Bros Studio Tour – The Making of Harry Potter, attractions, events, availability and pricing from £53.50 a head, enjoy a spell at the official website.