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The model was built for the first film – Harry Potter and the Philosopher’s Stone – and has been used for exterior shots in every film since.

When all the time spent by 86 artists and crew members is added up, it took an incredible 74 years to build.

Measuring 50 feet across, it has more than 2,500 fibre optic lights to simulate lantern torches and students passing through hallways.

It even has miniature owls in the Owlery and hinges on the doors.

The castle, which was based on Durham Cathedral and Alnwick Castle, is now due to go on display as part of The Making Of Harry Potter studio tour at Leavesden Studios, near Watford.