‘Consider the pace at which the story unfolds. Nobody is in control of it, which means it occasionally gets quite dull. We can’t fast forward or time-switch. We’re not invited to phone in and vote for which suspect we would like to see arrested. Key scenes and pieces of information are kept from us in a way that would defeat the point of a show like Big Brother. But we find this all the more compelling. The one nod to conventional broadcasting principles is that the ratings have mattered right from the beginning. When there was a risk that they might slump, David Beckham was drafted in to speak on the matter, thus giving the story a new boost. Most grippingly of all, we have no idea what genre of story we are watching, so have no idea how or when it might end.’

Suddenly we have to hold two entirely contradictory thoughts in our head at the same time. For the McCanns have now either suffered the cruellest fate imaginable - not only to have innocently lost their beloved daughter but also to have been publicly accused of a wicked crime - or they are guilty of the most elaborate and heinous confidence trick in history, deceitfully winning the trust and sympathy of the world’s media, a British prime minister, the wife of the American president and even the Pope, to say nothing of international public opinion. One of those statements, both of them extraordinary, describes the truth. As a senior tabloid journalist put it to me yesterday: “They’re either the victims of a horrible smear which they will never fully escape or they are cold, psychotic killers” responsible for the death of their own child.