BBC News By Russell Padmore Published Nikki from London has had the catalytic converter stolen from her car three times. "The second time it happened there were 11 or 12 vehicles locally that were also targeted overnight," she told the BBC's World Business Report. "The perpetrators can be quite violent, a family friend was attacked by the thieves when he tried to stop them." Another victim in London, Mark, explains how he confronted people he suspected of tampering with his car: "They got in a car, slammed the doors and pulled away. "I was concerned they had done something to the car, so I started it and it sounded like a tank. They'd managed to saw off the catalytic converter."