'I felt the surge of the shock. It was incredibly painful'

Michael Todd, Chief Constable of Greater Manchester, volunteered to be a "victim" to show how its 50,000 volts could be used as a weapon to tackle crime.

He was challenged to take the test earlier this month after he told a Police Federation conference in May he would be a guinea pig for any test of the device to back up his call to issue it to more officers. He was accompanied by two officers ready to catch him when a member of the Tactical Firearms Unit fired two metal barbs into his back from a distance of 10 feet in a trial earlier this month.

As the 50,000-volt charge was delivered through fine wires connecting the darts to the yellow plastic gun, Mr Todd screamed out "Aargh! Aargh!" in agony for five seconds. His face contorted into a grimace, his back arched, then he fell forward and was caught by the two officers who held him securely as his body convulsed for two or three seconds.

But within 20 seconds of being hit, Mr Todd, 45, was able to speak normally as a paramedic removed the barbs and swabbed the small puncture wounds.

Forty-five seconds after impact, he was helped to his feet and described the experience as the most painful of his life. "It hurt like hell," he told the Mail on Sunday. "I felt the full surge of the shock from my fingertips to my toes. At the point of impact I felt the barbs going into my back. Then the charge hit me. I wanted to fall forward but I was absolutely unable to move. It was incredibly painful."