An audience member claims he was injured in 2013

US magician David Copperfield has been forced to reveal the secret of one of his signature tricks, after being sued by an injured audience member.

Gavin Cox, from Kent in the UK, claims he suffered lasting brain and body injuries after agreeing to take part in the "Lucky #13" illusion in 2013.

Mr Cox says he fell over while being led through a secret passageway at the MGM Grand in Las Vegas.

The 57-year-old and 12 other volunteers were taking part in an illusion in which they appeared to vanish on stage, before re-emerging later at the back of the theatre.

He claims he was injured when he was "hurried with no guidance or instruction through a dark area under construction, with cement dust and debris causing him to slip and fall".

Illusionist David Copperfield (left) listens to questions from attorney Benedict Morelli (right) in a Las Vegas courtroom | Image: John Locher/AP/Press Association Images

The audience member was taken to hospital with a dislocated shoulder but claims he suffered chronic pain, headaches and confusion when he returned to the UK.

He's seeking unspecified damages in the lawsuit, which also names the MGM Grand, show producer Backstage Employment and Referral, and building firm Construction Management.

Gavin Cox (left) claims he was injured during an illusion by David Copperfield at the MGM | Image: Michael Quine/AP/Press Association Images

The court heard how the Lucky #13 vanishing act starts with the audience members in a cage.

A curtain is then drawn around it before assistants lead the volunteers through passageways, out of the venue, back indoors, through an MGM Resort kitchen, and then into the rear of the theatre.

They then make a dramatic reappearance during the finale.