There is no cavalcade, no parade, no men in braid. Just an old boy in a trench coat wandering alone down windy streets. He could be any lost American tourist.

Except this is Manchester and he is attracting way too many gawpers: “I have had a row with my mate,” burbles a taxi driver. “I swore I just saw Colin Powell, but my mate said, ‘What would he be doing in Manchester?’” A fair question. One Powell — until recently among the most powerful men on the planet — must have asked himself when the taxi collecting him was too small for his luggage. The general who held the world enthralled at the United Nations when he produced “irrefutable and undeniable evidence” that Saddam Hussein had weapons of mass destruction is now on the speaking circuit.

He has spent the past week in Britain, and whenever he orates you are reminded why he had been so damned persuasive. Outside his hotel there are protesters, but inside only eulogies.

Everyone respects Powell: the one Bushite who even Euro cheese-munchers thought they could do business with. Iraq might have left him isolated in the Bush administration, but he is the war’s only politician whose reputation didn’t take a hit. Powell oozes charm. As guest of the Jewish National Fund he smiles through an excruciating rendition of Imagine (strangely missing the line about imagine no religion) before he does his stuff — brilliantly.

He recalls how, in the run-up to war in Iraq, whenever he felt exasperated with France he had to remind himself: “France has been with us since 1776, and we have been in marriage guidance ever since.” He recalls a Kremlin showdown with Mikhail Gorbachev, who suddenly smiled and said: “General, you are going to have to find yourself a new enemy.” To which Powell thought: “I don’t want a new enemy: I am happy with the one I got.”

Having retired as secretary of state he no longer needs to be the constant diplomat, so in our interview he speaks frankly of his disagreements with George W Bush and his doubts about British intelligence. He almost giggles over how he saw off Jeremy Paxman in a recent interview: “I’d heard of his reputation but I think I escaped with a nil-nil draw.”

Next year he will be 70 but the married father of three grown children remains a powerful physical force: broad as a tank with searching almond eyes. The old warhorse doesn’t do retirement: “I’m busy: I don’t play golf.”

His presence turns minds to war: does the ramping up of pressure on Iran remind him of the build-up to invading Iraq? “The parallel is both countries pursuing a nuclear programme: the big difference is there is little dispute this time over the evidence.” Yikes.

Isn’t the irony that Iran is a greater threat than Iraq but after the political deception and military stalemate there is no appetite for aggro this time? “Even if there hadn’t been Iraq I do not believe there would have been an immediate leap from anyone for military action. I’m fascinated everyone here wants to talk about military options: just slow down. Iran is some years off a nuclear weapon. One of the papers said ‘if they had the material they could (make bombs in a couple of months’; well, they don’t. If I had the material, so could I.”

He may be sanguine but after the rift on Iraq with “old Europe” he can’t resist a dig at Euro efforts to cow Iran. He calls the unsuccessful European foreign ministers who have been involved in the negotiations, including Jack Straw, “my three tenors”: “They wanted to take the lead so I said, ‘Fine, it might even be better if (Americans) are not seen as part of your group’, and they came up with a couple of agreements, but they did not hold. Dr (Condoleezza) Rice (his successor) gave more support to EU efforts but it still didn’t produce results.”

However, Powell offers scant alternative. He even cautions against mild sanctions: “Banning sports tends to disappoint athletes, who are not building nuclear programmes. Rather than being mad at their regime they might be mad at us. Plus the Iranians have no doubt had their own national security council meetings and have factored in likely sanctions.”

His wry scepticism about European posturing also comes through when talking about “rendition”, where America shuttles terror suspects to Third World interview centres to loosen tongues. After an outcry Straw wrote to Rice demanding details of exactly when and where prisoners had been taken, but Powell suggests the foreign secretary and the “tenors” knew the score all too well: “Such things have benefited us and Europe. To suggest renditions are such a shocking thing to everyone’s sensibilities is a bit much. There are two parties to a rendition, if not more. So I thought Europe overreacted.”

We turn to Iraq. America initially sought war simply to oust Saddam; it was Tony Blair who ramped up the iffy intelligence about weapons of mass destruction. What did Powell make of Blairite claims such as Niger being in the market to supply Saddam with material to build a nuclear bomb? “I believe the British government still stands by that.” Which is amazing! “Yeah. I didn’t use Niger, except perhaps once early on at Davos. It just didn’t hold up.”