Throughout most of its history since the Second World War, the United Kingdom has conducted foreign affairs in such a way as to secure the country's interests while maximising its influence in a world dominated by Russia – the Soviet Union as was – the USA and China.
Whether we liked it or not, the declining power of Britain underlay what might be described as the diplomacy of pragmatism, where this country did what it could to make its mark, but accepted that Britannia no longer ruled the waves, and consequently had a reduced global influence.
With his action in leading the UK into Iraq, Mr Blair put an end to pragmatism in diplomacy and replaced it with a quasi-religious belief in the need for this country to follow, unquestioning, the lead taken by a Republican US president, George W Bush, who was driven by a zealot's belief in the rightness of his cause and prepared to back up this view with military action.
So it was that Britain became embroiled in the invasion of Iraq, with Mr Blair making his case based on the false claim that Saddam Hussein's access to weapons of mass destruction (WMD) posed an imminent threat, an assertion that will be one of the many points he will have to answer to Chilcot for.
Those who think that the former prime minister will back down are likely to be disappointed, for he has stated recently that, with or without WMD, he would still have wished to remove Saddam – further evidence, were it needed, of his ideological approach to foreign affairs.
Most observers now agree that Mr Blair's approach was disastrous for Britain and there is an interesting comparison to be made between his approach to Iraq and that which is slowly, very slowly, being adopted in relation to Afghanistan.
Yesterday's international conference in London on Afghanistan saw the beginning of plans for a military withdrawal by the Nato allies, including Britain and America, as strategies were put in place to strengthen the Afghan armed forces.
But alongside there was talk – from President Hamid Karzai, in particular – of trying to lure Taleban fighters away from the insurgency against his government with job offers underwritten, it appears, by money provided by the allies.
Put this along with a new focus on Pakistan, which is where al-Qaeda has moved now it has been driven from Afghanistan, and less emphasis on the idea of imposing our system of Western democracy on the country, and a pattern begins to emerge.
Not that British troops are about to leave Afghanistan any time soon – there could be a presence there for many years – but that we are beginning to be more realistic about our goals and what can, and cannot, be achieved. After Mr Blair's aberration, we should welcome a return to a new era of pragmatism.