This year marks the 15th anniversary of Harry Potter and the Philosopher’s Stone being published in the United Kingdom by Bloomsbury.

To commemorate the occasion, the publisher is launching a big contest to find the biggest fans.

They are requesting the help of booksellers and librarians to find who they’re looking for:

Much of Harry Potter’s early success was due to the support from brilliant booksellers and librarians, and Bloomsbury would love to call on that fantastic support once more.

Bloomsbury is inviting fans to write a letter explaining why they love Harry Potter. The only way to enter the competition is to post these letters in specially provided Harry Potter post boxes in their local bookshop or library. The competition will run from Tuesday 26th June until Tuesday 31st July 2012, after which we will select the winning entry and name the UK and Ireland’s biggest Harry Potter fan.

You can see a map of all participating stores and libraries on Bloomsbury’s site. Prizes include a trip to the Wizarding World of Harry Potter theme park in Orlando.

Good luck to all who enter!