When Archbishop Desmond Tutu refuses to share a conference platform with Tony Blair, this is seen as very bad news for the former prime minister. When Tutu goes on, in an article for the Observer , to suggest that "in a consistent world" Mr Blair would be on trial at the International Criminal Court in the Hague for his role in the Iraq War, it's guaranteed to get headlines. Jon Snow tweeted  that Blair might, in future, have (like Henry Kissinger) to be careful about his travel plans. At the very least, thought Snow, Tutu had "holed Blair's comeback desires below the waterline".
As the response posted on Blair's official website  noted, with some weariness, it's "the same argument we have had many times with nothing new to say." Whatever his other achievements (winning three elections, peace in Northern Ireland, winning the Olympics) Blair will never shake off Iraq. These days, he can't even appear at the Leveson inquiry without without someone slipping past security to denounce him as a war criminal. Nevertheless, an attack from Desmond Tutu carries particular resonance.
The archbishop's moral authority stems, of course, for his work as an opponent of the Apartheid regime, which won him a Nobel Peace Prize in 1984. But in recent years he has ranged more widely. As a sort of freelance international statesman he has been outspoken in support of everything from gay rights to climate change. In old age, Tutu possesses a particular kind of international clout, shared with very few others - Nelson Mandela certainly, the Dalai Lama probably, at a pinch Bob Geldof, but probably not the Pope - that enables him to call out world leaders on their political or moral failures and in the process cause them major embarrassment. It's a peculiar sort of soft power that owes little to any formal position and everything to personality, an image of "saintliness" and a high media profile. Tutu has never been afraid to use it.
As for Blair - he would love to have that kind of authority. There's little doubt that he still sees himself as a moral force in world affairs, through his work with his eponymous Faith Foundation, his role as a Middle East peace envoy and in his speeches, which often return to the theme of an international community united by common values which he seems to feel he is in a unique position to articulate. He aspires to be part of an international club of the great and the good, not just a former leader but a player in the same game of moral leadership as Tutu himself. His enthusiasm for moralistic language remains undiminished. But Tutu's status will forever elude him, partly because people remember what he was like as a politician, party because (unlike Tutu) he has never suffered, but mainly because of Iraq. A war that he remains utterly convinced was right in principle - indeed, an exercise in international morality.
That's his tragedy.
Tutu wasn't directly calling for Blair to be hauled off to the Hague. Nor does he have the authority to issue an international arrest warrant. Rather, the archbishop was complaining about the double standards of an international community that condemns Robert Mugabe while inviting Tony Blair to pontificate about "leadership". "Leadership and morality are indivisible," claimed Tutu. "Good leaders are the custodians of morality." By pursuing war based on "fabricated" claims about Saddam Hussein's alleged weapons of mass destruction, and then offering no "acknowledgement or apology" when "found out", Blair had forfeited his right to pose as an exemplar of leadership. Tutu even asserted that "the question is not whether Saddam Hussein was good or bad or how many of his people he massacred", but rather the morality of Bush and Blair in prosecuting the war.
Blair calls this suggestion "bizarre", and indeed it does seem to draw a wholly false moral equivalence between a murderous dictator and a democratic, if flawed, politician. But then Tutu was not being asked to speak alongside Saddam Hussein. His most cutting point was a personal one: he felt, he wrote, "an increasingly profound sense of discomfort" about sharing a platform with a man who had taken his country to war "on the basis of a lie", a war that had had catastrophic consequences for Iraq and the wider Middle East. That's got to hurt. What it means, after all, is that Tony Blair does not belong in his club.