In an era of relentlessly on-message machine politicians, programmed by press releases and party whips, there’s no doubt that the last London mayoral elections were a breath of fresh air for fans of the political maverick.

But whereas Boris was then known mostly for his stints on Have I Got News For You and upsetting Liverpool, Ken Livingstone’s career stretches back decades. A constant thorn in the side of Thatcher during the 1980s as leader of the Greater London Council (at least until she went for the nuclear option and abolished it), Livingstone has courted controversy on everything from the IRA to bendy buses, and famously became The Sun’s "most odious man in Britain".

I’ll declare my interest upfront: I’m a fan, and could even be found back in 2008’s drizzly April evenings handing out leaflets to commuters on behalf of Livingstone’s (sadly doomed) re-election campaign. But even if you hate his guts, you can’t deny that he speaks his mind.

“I’d most probably have been smoother if I’d gone to university,” Livingstone admits. “My parents’ only ambition wasn’t that I should be the first in our family to go to university, it was that I should be the first to have a pension.”

Mission accomplished, then, but Livingstone is still not planning on retirement. It’s well-known that he plans to run again for the mayoralty in 2012, and I wonder if another election as an independent might be on the cards if he doesn’t secure Labour’s nomination. “The problem isn’t going to arise,” he assures me, referring to the ‘ballot-rigging scams’ of 2000 when Blair desperately sought to prevent his candidacy. “Who wants to be Frank Dobson the second?”

I push for a firmer answer. For the benefit of any doubt, if he doesn’t get the nomination, he won’t run? “There’ll be a straightforward vote of party members and I’ll  accept the result of that ballot.” Which seems clear enough on the face of it, although seasoned Ken watchers will have their doubts.

If he did end up back in the mayoral chair, it wouldn’t be much fun without any money to spend, would it? “Well, if there’s a Tory government, I should imagine I’ll get very big rewards from the Prime Minister and the Cabinet for having got rid of Boris. Because he’s a threat to them.” This might seem rather outlandish, but then again, it’s not exactly hard to imagine a cabinet full of ‘day-dreamers’ wishing to succeed Cameron and wanting Boris safely out of the way.

So a Tory victory would be a rather good thing for Livingstone, all things considered? Unsurprisingly, he isn’t complimentary about the prospect. “You’ll have completely inexperienced youngsters trying to run government for the first time... and there’s a really hard-faced nasty group of swines lining up to get on the Tory benches, who look like they’ve done very well out of the last great surge of banking excess.”

Ah, the recession. I put it to Livingstone that two years ago he was predicting that there wasn’t going to be one, and half expect he’ll get defensive and quibble with my wording. But he doesn’t. “So what was wrong in that analysis?”

“I’d come to think governments had got better at working the cycle, but of course, they always pump money in but they never take money out, so they created this huge bubble. When you’ve been predicting a great crash for twenty years and it hasn’t happened, you do begin to think that you might be wrong. Just then, just as I gave up, it happened.”

Another great crash in London recently has been that of the career of Ali Dizaei. A Metropolitan Police commander, Mr Dizaei was convicted and jailed earlier this month on corruption charges, including assault and false arrest. (He has since declared his intention to appeal.) The founder of the Black Police Association (BPA) complained that Dizaei had used the organisation as a ‘fig-leaf’ to deflect any criticism as the product of bigotry and institutionalised racism.

“No no no...,” Livingstone insists, “he got away with it because a jury cleared him of corruption in 2003. Most people at the top of the Met, and myself, were surprised he got away with it.” So Livingstone had his own concerns? “I think everybody who worked with him was worried about him. But he’d have gone straight for discrimination and damages if the Met hadn’t accepted the verdict. There was also pressure from Blunkett. I might have been prepared to dig in, if it had been my decision, but it wasn’t.”

Does Livingstone not accept, then, that Dizaei was able to use the BPA for his own ends? “No. We ignored the BPA, because their demands were unreasonable. They went right off the rails in the last couple of years of my mayoralty, and that was the end of them – they lost their influence.” He does follow up by predicting their likely recovery, post-Dizaei, and stresses the importance as an organisation to have around. But Livingstone has clearly lost none of his willingness to speak out against former allies, which I suspect has been a crucial part of his political longevity.

Underneath this hard-nosed streak, however, lies a refreshing willingness for imaginative thinking and a sense of fun. What other mainstream politician, still aiming for electoral success, would be willing to muse happily on the prospect of a ‘United States of Europe’ or an independent city-state of London? “We’d be in the G20 – and we’d be exactly at the mid-point in population terms of 200 countries in the UN. The rest of the United Kingdom would have to change their money and their watches as they came over the border from Surrey... and we’d be happy.” And then, without pausing for breath, he’s back to how Manchester might improve its tram system.

Ken might be out of power for the moment, but even his strongest detractors would be foolish to write off this long-lasting maverick for good.