April 13, 2013 - 15:49 BST hellomagazine.com Kate Middleton, Prince William and his brother Prince Harry will take a tour of the Making of Harry Potter at the Warner Bro. Studios with members of their charities Kate Middleton, Prince William and Prince Harry have added a rare joint engagement to their diaries. The royal trio will attend the inauguration of Warner Bros. Studios on 26 April, where they will be given a tour of the Leavesden studios with around 500 guests from their charities.The Duke and Duchess of Cambridge and Prince Harry will be present for the official inauguration ceremony, where Prince William will give a short speech before heading on the tour to enjoy the studio's delights with their guests. According to St James's Palace the royal visit to The Making of Harry Potter exhibition will include a wand lesson in The Gryffindor Common Room and a special effects demonstration on the set of wizarding shopping street, Diagon Alley. Princes William and Harry and Duchess Kate, who will be over six months pregnant by the time of the visit, will then host a meeting for their Charities Forum in the original set of the famous Great Hall. William, Kate and Harry will be given an insight into the film making process and get the chance to marvel at props and costumes used in a throughout the blockbuster film series. The Hertfordshire studio tour will be Kate's third engagement of the week, following visits to a Manchester primary school on 23 April and a return to the National Portrait Gallery on 24 April.