Idris Elba is urging the British government to ban machetes and serrated “zombie” knives to help stop young people falling victim to knife crime. The London-born star of iconic television dramas, The Wire and Luther joined protesters from the “Don’t Stop Your Future” campaign on Monday (9 January) outside Parliament, posing with clothes and shoes representing people killed by knives. In the UK, which has strict gun-control laws, about four in 10 homicides involve a knife or sharp instrument. There is particular concern about knife crime involving young people in Britain’s cities. In London, 21…