Warner Bros will open its “ The Making of Harry Potter ” walking tour at Leavesden, England, the production base of the Harry Potter films , in spring next year. The three-hour-long tour will give fans the chance to see sets, costumes, props and effects used in all 8 Harry Potter movies. Tickets go on sale later this year. Potter fans will be able to walk onto sets including headmaster Dumbledore’s office and the 120ft long Great Hall featuring “the tables and benches used in the films”. The studio tour, first announced last November, is part of Warner Bros’ $161M refit of Leavesden, which is set to be one of the largest studio production facilities in Europe when it opens. Warner Bros plans to use the 250,000 sq ft of soundstages to shoot its blockbusters. The studio won’t be ready for Chris Nolan shooting The Dark Knight Rises this year though. Leavesden will also boast the largest back-lot in Europe. Around 1,500 people are employed at Leavesden when production is in full swin