The secrets of world-famous illusionist David Copperfield's show have been exposed in a long-running legal battle.

The Daily Mail reports how London-born chef Gavin Cox is suing the world's most famous magician, claiming he was left with permanent brain damage as a result of an illusion that went wrong at his Las Vegas show.

Cox, 55, was called on stage by Copperfield at the MGM Hotel and Casino to take part in a disappearing audience illusion in November 2013, only to fall backstage mid-way through the trick.

Now the secrets behind the famous "vanishing crowd" trick have been revealed in extraordinary detail, court documents in the three-year legal battle show.