Can David Cameron use the debate over the riots in English cities to reinvigorate his premiership? Given the damage done by the violence itself, as well the subsequent rows between the UK prime minister and police leaders, it might seem like an odd question.

Yet three weeks ago, when parliament packed up for the summer, Mr Cameron’s leadership was badly tarnished by the phone- hacking scandal and his ill-judged hiring of Andy Coulson, the former News of the World editor. Those misjudgements over phone hacking still cast a shadow over him, but the riots have changed Britain’s political landscape. The subsequent debate offers Mr Cameron an opportunity to relaunch himself – if he can seize it.

In his initial response to last week’s mayhem, Mr Cameron acted belatedly, but competently. He is often at his best in a crisis. When the scandal over MPs’ expenses erupted in 2009, he was quick to purge miscreants in his own party. Last week, his words and deeds – recalling parliament, setting up all-night courts, expressing concerns about “sick” parts of British society – matched the public anger over the scenes of destruction.