As late as Tuesday morning NZT, No 10 was arguing that there was no need from him to return. By that time trouble had broken out in Hackney and Lewisham and shops across the capital, from Barnet to Croydon, were closing early in anticipation of violence.
There was an air of panic as Cameron was finally scrambled on to a military aircraft back to Britain and a meeting of the Cobra emergency committee.
He decided to throw resources at the problem - more than doubling the capital's police presence. It was a move that would have been welcomed 12 hours earlier in areas such as Clapham, Woolwich and East Dulwich, where looters went unchallenged much of the night.
He will hope that the sheer force of police numbers will ensure the disturbances are short-lived.
If he fails, Cameron will face searching questions over his competence.
The Mayor of London, Boris Johnson, faced furious heckling from residents clearing up wrecked parts of south London as he returned from holiday to try to salvage his administration's battered reputation for competence.
Clutching a bright green broom, he proclaimed the "real spirit of London" during a walkabout in some of the worst affected parts of the capital. But he faced a barrage of angry taunts and questions from people helping the clean-up operation in Clapham.
"Why are you here now," shouted one. "It's too late."
Fighting to be heard above a growing crowd demanding answers, Johnson, back from his holiday in Canada, said: "I want to say first of all to everybody who owns a shop, to everybody who owns a business here, how very sorry I am for the loss and the damage that you have suffered."
Johnson said he understood that there were questions about the police response, but promised that the perpetrators would be "punished".
Johnson faced chants of "How was your holiday, Boris?" as he tried to condemn the violence.
- INDEPENDENT