As Chilcot showed, Tony Blair was a 20th-century leader in a 21st-century world

King Philip II of Spain, the dominant ruler of 16th-century Europe, sent the armada to its defeat, lost the Spanish Netherlands to the Dutch and spent large parts of his reign persecuting heretics. Yet it was said of him that “no experience of the failure of his policy could shake his belief in its essential excellence�.

Listening to Tony Blair on Iraq this week, one heard the same undeflected certainty in defiance of the facts. Say what you will about Blair, but he is at least consistent. He gave essentially the same defence of the invasion of Iraq this week as the one he gave to MPs and the public 13 years ago. But at its heart, just as with Philip II, was the same political flaw: the obdurate belief of a leader that the virtue of the policy, as he saw it, transcended its all too evident failure.

In the end, what matters about Blair’s Iraq policy was not whether it was right or wrong, though in my view it was always the latter. Blair never properly understood the neocon agenda of the Bush administration or the limits to the significance of the 9/11 massacre. He mistakenly believed Labour’s credibility with the British people depended on standing shoulder to shoulder with Washington in all circumstances, even under George W Bush. And he blinded himself to the limits of British military effectiveness.

What really matters about Blair’s Iraq policy is that, as the Chilcot report explicitly says, it didn’t work. Blair is still in denial about that. Yet it has not taken 13 years to discover this failure. The policy failed at the very moment the Iraq war began. The failure to secure a second UN security council resolution against Iraq in March 2003 should have been decisive. But it was brushed aside.

A better leader would have recognised the profound significance of that failure. That was the moment Blair could and should have said: “I support the Americans, but I cannot go to war alongside their unilateral action. I regard this as a tragic error by both Washington and the UN that the world will come to rue. It breaks my heart, but I cannot recommend war on this basis. Our troops will not go into Iraq.�

It is possible that this policy failure would have brought Blair down, but I doubt it. Blair was a very popular leader in 2002-03. He would have been derided by the Conservatives and their press. But he also had real public standing. A decision to stand the troops down would have been widely welcomed and given his support a shot in the arm.

And events would have soon been on his side. Assuming the US invaded Iraq anyway, which it would have done, the failure of the occupation would have made the climbdown seem prescient. Long term, Britain would have paid a smaller price in Washington than Germany or France did for the same failure to join the invasion. In Europe he would have been the man of the hour.

But Blair was not that kind of a leader. In part he refused to admit failure – but he also pretended to himself that failure did not matter. Failure even seemed to strengthen his conviction that he was right. He set off on the tragic journey towards public isolation and contempt in which he now finds himself stuck.

This week Blair sought to portray public hostility as the necessary scar to be suffered for brave leadership. It is no such thing. Paraphrasing Talleyrand, I regard Blair’s Iraq policy as an error, not a crime. But it was a terrible error all the same. It cannot be justified by the sincerity, let alone the naivety, of the decision that caused it. Blair should heed the awful words of the old Bolshevik imprisoned in Stalin’s gulag in Vassily Grossman’s Life and Fate, who says simply: “We made a mistake. And this is what our mistake has led to.�

Philip II could withstand a bad failure of policy because he was an absolute monarch. Politicians have to be answerable for failure in ways that autocrats are not. In many respects David Cameron is not Blair’s equal as a politician, but he was right to accept responsibility and resign after the Brexit vote, which is the worst thing to happen to this country since the Iraq war.

In the first part of his 13 years as Labour leader, Blair redrew the template for modern British political leadership. He was comfortable with the modern, at ease with change, pragmatic, sensible and effective. He appeared a paradigmatic leader. Cameron was in awe of him. Michael Gove calls him the master. In retrospect, though, Blair now appears a more transitional leader.

He ran the Labour party from the top down, as though it were still a big machine, albeit no longer the kind of machine it was in Harold Wilson’s era. So did Gordon Brown. Different in so many ways, neither was at ease with consultation or democracy, formal or informal. Both Blair and Brown struggled with the reality that parties, Labour included, were in decline – and parliamentary politics was losing respect.

Social media and 24-hour news were new power centres. Yet Blair saw – and still sees – himself as an authority leader in a very 20th century mode. His instinct for running against what his party wanted was in part an attempt to acquire a version of the authority that would have gone with the job in earlier times. That too was sacrificed on the altar of Iraq.

Political leadership in the 21st century requires different skills. Politicians are struggling to find ways of turning these to lasting account. It isn’t easy. Boris Johnson’s implosion shows how celebrity is not the answer. Jeremy Corbyn’s failure shows that authenticity and purity are not enough. Authority and standing are still essential attributes, but they do not come from hard power as much as from soft-power skills, problem-solving, cooperative approaches and personal self-restraint. Women are often better at this adaptation than men, though as always it depends on the individual and the skill set.

The successful politicians of the age are people like Angela Merkel, potentially Justin Trudeau and perhaps – it may be premature to add – Theresa May.

Merkel possesses immense staying power precisely because she does not try to solve the world’s problems in the grand sweeping way that Blair or Brown preferred. Instead she responds practically, is willing to change things that do not work, cultivates her own individual ordinariness, and stays out of military adventures. Unless Blair can rethink, which seems unlikely, his unshakeable beliefs now have little to offer in the search for effective political leadership the 21st century way.