Fourteen-year-old Martin Dinnegan sensed he was in danger when a group of boys pulled faces at him on a London bus. An hour later he was dead, stabbed in the back by the same gang that pursued him after he got off at a bus stop, according to dpa. Teenagers posturing in front of victims, and being ready for violent confrontation were now the "scourge of cities and towns," the prosecutor dealing with Martin's murder said. "This is such a case, which leads from dirty looks to death in one hour," he added. Safety on London's buses has been in the public eye ever since Anthony Whelan, 28, was stabbed to death on the top deck of a double- decker in the summer of 2005, trying to shield his girlfriend from having potato chips thrown at her by a fellow-passenger. The capital's new mayor, Boris Johnson, has pledged to place plain-clothes officers on trains and buses, where a ban on consuming alcohol is to come into force on June 1. But escalating knife crime, which has claimed the lives of 15 teenagers so far in London this year, is not confined to vandals rampaging on a driver-only bus, it has also reared its head outside schools and bars, and even on Oxford Street, the city's main shopping quarter. Among the recent victims of the killings, which affect all ethnic groups, was 18-year-old Robert Knox, a young British actor with a role in the next Harry Potter movie. "With every teenage death a little bit of London dies too," said Kit Malthouse, London's deputy mayor responsible for the fight against youth crime. A recent survey showed that more than one in every 10 young people has been affected by gun and knife crime, and that 36 per cent of all youths were afraid of being the victims of such crimes. As metal detector arches mushroom at Underground (Tube) and railway stations, and police officers with hand-held scanners are deployed at school gates, London's Metropolitan Police have enlisted young victims of muggings and knife attacks to help them in the fight to take the "glamour out of knives." A new hard-hitting campaign, devised with the help of 18 young people affected by such crime, show images of horrific real-life knife wounds suffered by victims. The real images from a medical photo library, as well as CCTV footage from a shopping street stabbing will be distributed through social networking websites and on mobile phones. One such image, showing a mutilated hand, is accompanied by the warning that carrying a knife makes the bearer more, and not less, vulnerable to attack. "I hope it will make people think twice about using a knife," said 16-year-James Turton, who designed the poster after he became the victim of a mugging. The message was aimed at burying the belief that carrying a knife makes makes you feel safer, a reason given by most young people in surveys about knife crime, according to police. "It is of critical importance that young people understand that carrying a knife is not cool," said London's police chief Ian Blair. For parents, the time had come to talk to teenage children not only about "drink, drugs and relationships, but also about knife crime." However, with a recent survey showing that two-thirds of 800 youngsters cited drugs, self-protection, image, peer pressure and revenge as reasons for becoming involved in gun and knife crime, the police knows it cannot win the battle on its own.