Former Prime Minister Tony Blair has been roundly – and rightly – criticised for his attempts to rewrite history on Iraq. He says his decision to support the US invasion of the country in 2003 was correct and played no part in the savagery now taking place in that benighted country.
Indeed, if he had his way, the Western nations should now be bombing Syria as he argues that that country and the disintegrating Iraq pose the greatest threat to the West. It is now fundamentalist terrorists rather than weapons of mass destruction that we should fear.
Current Prime Minister takes a more pragmatic and sensible view of the way forward.
He realises that there is only one country which could really influence events in Iraq, and that is the West's former nemesis, Iran. But Iran is trying to rebuild relationships with the West, and Britain and America are willing to engage in the process, if only to avoid the blame if Iraq's sectarian war spirals totally out of control.
It is a sad irony that the medieval savagery of Isis could bring about an unlikely rapprochement between Iran, which not so long ago was beyond the Pale, and the West.
It is in both sides' interests to ensure that Isis does not make any further gains as it marches towards Baghdad.
Iran can also ensure that the Shia majority in Iraq does not seek revenge on ordinary Sunnis for the actions of the Isis extremists, sparking all out civil war.
David Cameron should heed his own words and rebuild the relationship with Iran step by step.
Practical diplomacy is a much better response to the current tinderbox situation in Iraq than simple military-based intervention.
The overthrow of Saddam Hussein may have got rid of a brutal dictator, but Britain and the US failed to establish a strong and credible alternative Government before leaving Iraq.
Perhaps an unlikely alliance with Iran will help to redress that mistake.