Normally anybody who criticises Jeremy Corbyn is guaranteed knee-jerk support by the British media which apparently feels that it does not even have to pretend to be non-partisan when it comes to the Labour leader. The only political figure similarly subjected to automatic demonisation is Tony Blair, so when he fiercely attacked Corbyn last week for supposedly focusing on “the politics of protest” at the expense of “the politics of power” it was interesting to see which man would be targeted.

Almost without exception, critics from Nigel Farage to Michael Moore denounced Blair as the root of all evil in the Middle East and beyond. Some claimed that he was so discredited that his views were no longer worth listening to, and others suspected that he was carrying out a pre-emptive strike before the publication of the report of the Chilcot inquiry, which is expected to criticise him severely for his actions in the run-up to the invasion of Iraq in 2003.

Tony Blair responds to war criminal claims with astonishing attack on Jeremy Corbyn

Ignored in these denunciations was the fact that Blair’s policy of foreign intervention did not end when he ceased to be prime minister but continues up the present day. David Cameron intervened militarily in Libya in 2011 with results that were just as disastrous as anything that Blair had been responsible for eight years earlier, and the Prime Minister has repeatedly expressed regret that he was thwarted by the House of Commons in his plan for airstrikes in Syria in 2013.

Blair’s periodic eruptions are so useful because he openly reveals that, like the Bourbons, he has learned nothing and forgotten nothing since the start of the Iraq war, while other western leaders pretend the opposite but in practice do much as he would have done. It is worth quoting his jibe at Corbyn – that jibe which generated so many headlines – because it perfectly encapsulates not just his own misjudgements about “the politics of power” in the Middle East, but the misconceptions of successive British governments. He said he was “accused of being a war criminal for removing Saddam Hussein – who, by the way, was a war criminal – and yet Jeremy is seen as a progressive icon as we stand by and watch the people of Syria being barrel-bombed, beaten and starved into submission and do nothing.”

In other words, Blair still favours foreign interventionism and believes it is effective and beneficial despite all the evidence to the contrary from Iraq, Libya and Afghanistan over the last 15 years. But it would be a mistake to think that here he is expressing an isolated opinion of his own because, for all his pariah status, much of the British media and a significant minority of his own party supported British participation in the US-led air campaign against Isis in Syria.

Cameron claimed that Corbyn’s opposition to airstrikes showed he was a terrorist sympathiser and the Shadow Foreign Secretary Hilary Benn made a much-lauded speech full of bombast about supporting British airstrikes against Isis in Syria as being equivalent of battling Franco in Spain in 1936 and Hitler in 1940. The degree to which this was phony posturing on the part of Cameron and Benn is highlighted by the fact that neither has shown concern that the RAF’s actions against Isis in Syria in the six months since the famous House of Commons’ vote have been very limited. Out of 3,787 airstrikes by the US-led coalition of air powers in Syria up to 1 June, only 237 were carried out by non-US aircraft.

Blair is an extreme and self-interested example, but there is still very little understanding among Western leaders about what happened in Afghanistan after 2001 and in Iraq after 2003. Whatever the humanitarian justifications for foreign intervention there, the wars rapidly transmuted into neo-imperial ventures not much different from those undertaken during the high days of imperialism in the 19th century. Even supposing that Blair is sincere in his oft-stated claim that the motive for the war in Iraq in 2003 was to overthrow Saddam Hussein, this is a simple-minded and misleading explanation of what really happened and what went wrong. Had the removal of Saddam and his non-existent WMDs been the real aim, and the US and British forces had immediately withdrawn once it was accomplished, then President George W Bush and Tony Blair might even have got away with it.

Debate about what happened commonly treats two crucial events as a single development when in fact they were separate: one was the invasion of Iraq and the other was the subsequent occupation of the country. The first objective was theoretically attainable had the invading powers been at any time honest about what they were planning to do, but once they had occupied Iraq and sought to rule it directly or through compliant proxies then they were bound to fail disastrously. By the summer of 2004, the US and its allies in Iraq fully controlled only islands of territory and were facing full-scale rebellions by both Sunni and Shia Iraqis. Once they occupied Iraq with large land armies and sought to become the predominant power there and in the region, it was clear that they could never succeed.

Much of this was obvious at the time for anybody on the ground in Iraq. I remember Hoshyar Zebari, the long-serving Iraqi foreign minister, saying to me then that the most important political fact was that none of Iraq’s neighbours agreed with the occupation or were prepared to accept it. A captain in British military intelligence in Basra told me that he kept vainly trying to explain to his superiors that the great difference between the British counter-insurgency campaigns in Malaya and Northern Ireland and the one in Basra was that “in Iraq we have no real allies.”

Fast forward 13 years and there is the same slack grip on reality when it comes to the continuing war in Syria and Iraq, and the same willingness to present a fantasy picture of the multiple conflicts there.

Blair is useful because he still believes that the removal of Saddam Hussein should have brought peace and plenty to Iraqis had there better reconstruction and pre-war planning after the invasion and if it had it not been for the malign intervention of Iran and Syria. He never takes on board that the US and Britain were seen as imperial occupiers by most Iraqis and that they were plugging themselves into sectarian, ethnic and regional conflicts which they could only make worse. He does not see how, among the many horrendous consequences of the war he helped start and has not stopped to this day, has been a vastly strengthened al-Qaeda and the establishment of Isis.