Expecto Patronum has been voted the favourite Harry Potter spell after the first official global search by JK Rowling's publisher, Bloomsbury Children's Books , as part of the celebrations for today's second Harry Potter Book Night, themed A Night of Spells.

With over 2700 votes, the Expecto patronum spell was followed closely by Accio in second place and Wingardium Leviosa in third.

One of the most famous and powerful spells, Expecto Patronum is key throughout the entire Harry Potter series of books. It first appears in Harry Potter and the Prisoner of Azkaban and is taught to Harry by Professor Lupin.

“Professor Lupin continued, ‘The Patronus is a kind of positive force, a projection of the very things that the Dementor feeds upon - hope, happiness, the desire to survive – but it cannot feel despair, as real humans can, so the Dementors can’t hurt it.

“But I must warn you, Harry, that the Charm might be too advanced for you. Many qualified wizards have difficulty with it.”

The spell has an added poignany now, as Vanity Fair recently reported. After the death of Alan Rickman, the actor who played Severus Snape, last month, a fan asked Rowling, “Will you tell us the piece of information that you told Alan Rickman about Severus Snape? Or will that forever be a secret?” and the author replied:

“Always” is how Snape explains to Dumbledore in the final book why his Patronus takes the same shape as that of his long-lost love: Harry Potter’s mother, Lily.

“‘But this is touching, Severus,’ said Dumbledore seriously. ‘Have you grown to care for the boy, after all?’ ‘For him?’ shouted Snape. ‘Expecto Patronum!’ From the tip of his wand burst the silver doe. She landed on the office floor, bounded once across the office, and soared out of the window. Dumbledore watched her fly away, and as her silvery glow faded he turned back to Snape, and his eyes were full of tears. ‘After all this time?’ ‘Always,’ said Snape.”

Schools, libraries, bookshops and community centres across Britain and Ireland will be creating their own events to celebrate JK Rowling’s series of books.

For the first Harry Potter Book Night last February, there were 10,500 parties and celebrations held all over the world. Harry Potter novel sales total more than 450 million copies worldwide, and they have been translated into 78 languages. Check out local events here.

The top 10 spells and what they do

1. Expecto Patronum – to summon up a Patronus

2. Accio – to call an object to you

3. Wingardium Leviosa – to levitate objects

4. Expelliarmus – to disarm your opponent

5. Lumos – to ignite one's wand-tip to provide light

6. Alohomora – to open locked windows and doors

7. Avada Kedavra – to bring about instant death

8. Sectumsempra – the incantation for one of the Half-Blood Prince's spells

9. Obliviate – to make the subject forget

10. Riddikulus – to make a Boggart take on a comical appearance and eventually explode