Now that Harry has hung up his Firebolt, Warner is looking to keep the multi-billion dollar franchise alive. Welcome to The Warner Bros Studio Tour London – The Making Of Harry Potter, a new attraction that opens today at its Leavesden studios in Watford, England. There, Muggles will get a glimpse at the behind-the-scenes magic of the films right where they were shot. As time wears on, however, it’s likely that interest in Potter will wane – but Warner says there’s a plan for that too.

When Warner Bros acquired film rights to JK Rowling’s Harry Potter, lore has it the author insisted on an all-British cast and that all films be shot in the UK. Ten years later, the highest-grossing film series in history has had a huge impact on the British economy – and on Warner Bros’ bottom line. In June 2010, London mayor Boris Johnson penned an editorial in The Telegraph decrying the fact that a Potter theme park was to open in Orlando rather than in Harry’s own backyard. He wrote: “This Potter business has legs. It will run and run, and we must be utterly mad, as a country, to leave it to the Americans to make money from a great British invention.”

Fast-forward 18 months and Johnson was waving a wand at Ollivander’s shop on the Potter tour’s Diagon Alley. A coincidence? Warner’s Sarah Roots, VP of the tour, tells me the idea of a film based attraction at the Leavesden studios has been in the pipeline for quite a few years and that Harry Potter has been such a part of the studio’s heritage, “it made sense to launch the attraction with Harry Potter.” The opening of the tour is timed to coincide with the start of Easter break for British school kids. Warner is eyeing up to 5,000 visitors per day on staggered tours that last about 3 hours. Roots says tickets for the first period have sold well and that first visitors are expected to be mostly UK residents with more overseas interest next year. As with all tourist destinations in the UK this summer, Warner is hoping for a residual Olympics effect.

Physical work on the tour project began in December 2010 when Harry Potter And The Deathly Hallows – Part 2 finished shooting at Leavesden and a month after Warner acquired the studios, announcing a more than £100 million investment to rebuild and expand the facility to serve as its UK base. The studio itself will open this summer and work was still continuing on the tour when I visited in February. According to Roots, a “significant amount” of money has gone to build the two new stages where the Harry Potter tour will live. Those stages, coincidentally labeled J and K, hold original sets that were used across the 8 Harry Potter movies. Unlike the Wizarding World Of Harry Potter attraction in Orlando, the studio tour is a behind-the-scenes look at how the films were made – there are no rides here.

Warners brought back production designer Stuart Craig and others to spiff up old sets including theMinistry of Magic, Dumbledore’s office, the Great Hall, the Weasley kitchen, the Potions classroom, Professor Umbridge’s office and many others. The tour begins in a screening room where a short film talks about the making of the movies. Once that’s over, the entrance to the Great Hall, where Hogwarts students and teachers dined daily, is revealed. The tour will be partly guided and also allow folks to wander on their own past sets preserved behind velvet ropes. There’s a demonstration of green screen technology and a creature effects workshop where I saw the giant spider Aragog (smaller in person), Buckbeak the hippogriff, Fawkes the phoenix and the Basilisk head. Visitors also get a look at the self-washing frying pan in action at the Weasley’s, the Sorting Hat and the Sword of Gryffindor.

Those involved are careful to note that the term “museum” is one they’d rather avoid. But the attraction is still more of a look-but-don’t-touch experience. Fair enough, I visited before the real interactive elements had been installed, but I still felt a bit disappointed. For my money, the most impressive aspect and the one that made me really feel a part of the movies, was the walk down Diagon Alley. You can’t go inside the shops since they’re just the original facades, but it was still a rush to stand outside Potage’s Cauldron Shop, Weasleys’ Wizarding Wheezes and Gringott’s Wizarding Bank. The Ministry of Magic hall was also pretty cool. The interactive elements include sitting in the Weasley’s Ford Anglia and having your picture taken (for £12) astride a Nimbus 2000 while wearing a Hogwarts robe in front of a green screen-projected scene. This probably explains why Warners believes the tour will take 3 hours. You could easily get through it in less time, but I suspect the wait for getting those pictures taken could start to feel like Christmastime at the mall with Santa.

The entire attraction is set on 150,000 square feet including a small backlot that will feature the Night Bus and a length of Privet Drive where Harry lived in the cupboard under the stairs.  It also houses a café and covered terrace where visitors can have a butterbeer. Since I visited, a scale model of Hogwarts Castle has been unveiled as another draw and sets, costumes and props not being used on the tour when it opens can eventually be switched in from the Warner archive. There’s a boutique that will sell chocolate frogs, golden snitches, house cloaks and Hermione’s dress from the Yule ball, among other branded items. And, there’s a Starbucks.

According to current pricing, a family of four will pay £83 pounds for entry (individual tickets are £28 per adult and £21 per child). But a little shy of two months out from the opening, local businesses had yet to implement promotional offers related to the tour and outdoor marketing was scarce. Arriving in London last Sunday, however, it was hard to walk a few feet without seeing posters encouraging visitors to book tickets online. Some partnerships exist including with Golden Tours, a bus operator that will pre-buy stocks of tickets and package them with ground transportation from London to the venue about 20 miles away. Further packages are expected to be tied to the Olympics. Roger Gagan, the chief executive of the Watford Chamber of Commerce tells me the tour is “creating a lot of interest around here and we’re looking forward to the open. We’re excited and delighted.” The town, he said, is eager for jobs that may be created by both the tour and the opening of the functioning studio this summer. “It will definitely bring other companies into the town, not only from this country but from abroad.” But since there’s nothing else really of note in Leavesden, it’s likely to be a quick day trip for most tourists.

While the tour is unlikely to generate similar sums, the overall effect of the Potter franchise on the British filmmaking economy is undeniable. British Film Institute statistics show that Warner boosted the local economy with about £1.9 billion in inward investment from 2000-2009, although that figure is not solely based on Warner’s Potter films. An oft-heard refrain when one posits that the lack of Potter films will have an adverse effect on the overall industry is that, to the contrary, their positive effect will continue to be felt for many years. A spokesperson at Film London contends the films haven’t left a gap at all, “rather, they’ve created a better skilled crew base if anything and made the UK an even more attractive prospect.” Post-production and effects companies like Double Negative, Framestore and The Moving Picture Company are among those roundly cited as having benefitted from the Potter boost. Half-year figures for 2011 were up 16% in terms of inward investment, despite the lack of a Potter film being shot. Movies that contributed to the nearly £700 million of spend in the first six months of 2011 included Warner’s The Dark Knight Rises and Dark Shadows along with Fox’s Prometheus.

The fact that it’s not just the Potter films that have helped boost the British economy is important because the zeitgeist is fickle. When Pottermania dwindles in earnest, Roots tells me Warner is prepared. “At the moment, the tour is 100% Potter but I expect that in a number of years’ time, we might bring in other Warner properties.” Those would likely include elements of the Sherlock Holmes or Dark Knight movies. “It’s always been the plan,” that other properties would make their way onto the tour, Roots says. But, she vows, “It will always have a lot of Potter.”