Evidence that the smell of fear is real was uncovered by US scientists last year who studied the underarm secretions of 20 terrified novice skydivers.

The researchers found that people appear to respond unconsciously to the sweat smell of a frightened person.

Scientists at City University London now hope to develop security sensor systems that can detect the human fear pheromone.

Team leader Professor Tong Tun told The Engineer magazine: 'The challenge lies in the characterisation and identification of the specific chemical that gives away the signature of human fear, especially the fear in relation to criminal acts.'

Don't fart near the detector