The colossal Harry Potter poster on the side of the National Media Museum is to be given away in a competition.

The Harry Potter and the Half-Blood Prince IMAX vinyl poster is as tall as two giraffes and as long as a whale. A museum spokesman said: “Harry Potter is going to be one of the biggest films of the summer so we are giving people the opportunity to win one of the biggest posters.”

To enter, people will need to answer the question: which of these Harry Potter characters is the largest: Hermione, Hagrid or Horace Slughorn? To enter visit nationalmediamuseum.org.uk.