How did Jamie Raven do his word trick on the third semi final of Britain’s Got Talent 2015?

How did Jamie Raven do his word trick that resulted in gold fish and an helicopter on the third semi final of Britain’s Got Talent 2015?

This is the question the judges are asking following a simply brilliant performance from Jamie Raven.

Jamie turned an empty box into a pack of cards and says he asked 52 members of the audience to name an object and write them down. He asks Alesha to choose four at random and gives the judges one word each.

Each judge had to reveal what was written on their card. David had goldfish, Amanda had Ice and Simon had helicopter. David then made each item appear in the most amazing way.