John McCain did not march to the front of the stage when he accepted the Republican nomination and declare that he was “reporting for duty”, as John Kerry, the Democratic candidate, did in 2004. But if he had, it would not have been a surprise.

Like his fellow senator and war veteran, Mr McCain used his party’s convention this week to focus his biography on a single life-changing experience: his years as a prisoner of war in Vietnam. In this narrative, presented at times in excruciating detail by some of the Arizona senator’s closest friends, everything about the man Mr McCain became and the kind of president he might be links back to the story of his capture and the torture he endured for five and a half years at the “Hanoi Hilton”.