'Has Johnson any politics? No. We just thought he did, based on a collection of crazed neocon rubbish he wrote for the Telegraph.' The truth, according to Ken Livingstone, is far worse.
'What's apparent now is that Boris only believes that people like Boris should run the earth. There's no political position he's not prepared to surrender in order to stay powerful. And that makes him very dangerous. In a situation where the far right, for example, could deliver him power, he'd have no hesitation in pandering to them.'
I meet Ken Livingstone in his new office - a window table in a Hampstead branch of Costa Coffee - and he is more than keen to chat. And not just about Boris. We talk about economics, about China and India and the organisation of gender roles before metalworking developed, about his plans for a roaring comeback and the future of the left. Ken talks and talks and his kind blue eyes twinkle and I feel faintly like I'm about to be invited to attend wizard school, albeit one with a little more pork-barrel canniness than anything invented by J K Rowling.
'When the prime minister asked me to run as Labour's mayoral candidate in 2004, I'd have been crazy to have said no. If I had, it would have been held against me, and against London, forever - but after I said yes, they had a duty to stand by me and my decisions. After 2004, the money flowed.
'Since then we've managed to invest £39 billion in London. I've left Boris the money for 50,000 new houses, which he might even build. And even if the mayor has only crude mechanisms to redistribute, doing small things to make working people's lives easier - cutting bus fares for people on income support, for example - that's what was most important to me about the job.' Ken knows better than anyone how crucial small but strategic changes can be - like Boris's first policy axe, the Venezuelan oil deal that provided cheap fares for London's poorest and environmental support for Venezuela's cities.
Ken Livingstone is a practical revolutionary, and he loves London with a deep and energising reverence. It's this love for the city rather than the City that breaks through when he speaks of the necessity of bank regulation. 'I'm a socialist, but it's not a question of socialism, it's a question of common sense,' he explains. 'Roosevelt did it in 1945, and then Reagan and Thatcher came along and ended 50 years of economic stability. It's taken a generation to take effect, but that's when this crisis started. And don't forget, the very same Tories who are clamouring against New Labour now were there when it started. They might have been in short trousers at the time, but they were totally committed to deregulation.
'It's important to remember about Cameron that, although he was only an oiky little nerd at the time, he was Lamont's adviser on Black Wednesday. Now Osborne and Cameron are once again talking of commitment to reducing the state - just as the world needs large state systems more than ever.
'For example, all European finance ministers have agreed that finance centres aren't casinos, except Britain. But if you operated responsibly, if you had even a one per cent tax on financial transactions, that would generate enough money to end poverty.'
It's about this point that Ken starts talking, very quietly, about a new project for the left - one that encompasses, however reluctantly, a world where workers' revolutions are a vanishing prospect.
'Every left activist has to understand that globalisation is inevitable: there are no national solutions any more. What's important is linking up the struggles in different countries. Debating voters' rights in the US and the UK; defending Venezuela and Cuba from US imperialism. Looking towards Europe, and towards China.
'I have a great deal of hope for China. It offers an alternative to the US's destructive form of capitalism. It's about to become the leading country in combating climate change. And we must remember that politics isn't about a choice between pure good and pure evil. It's about choosing the shade of grey that's the least grey.'
Listening to Ken talk about China is almost painful. It calls to mind a certain Olympic closing ceremony where this country was lately humiliated by a clown with an entitlement complex and his jacket flapping open. Ken knows all about China because he was supposed to be there. But whatever the papers say, any snippiness the conversation draws out is almost instantly overwhelmed by an infectious energy: energy for politics, energy for the next project, energy that turns bitterness into black humour. Retirement, for Ken Livingstone, doesn't mean golfing and easy domesticity. Like a true liberal politics junkie, everything comes back to the state we're in today.
'I'm writing my autobiography at present, and I've just got to the part where I'm about 17. It's horrendous stuff. I remember always being the weedy kid at school, always coming in on the mile run second last, just in front of the fat one. My sports teachers all seemed to be rehabilitated Nazi war criminals who believed that humiliation was a good way to make us improve. It wasn't.' Which brings us onto crime and the skills crisis.
'However much I hated them, the way school playing fields have been sold off over the past 20 years means that kids who aren't academic successes now have less to go to school for. And that causes problems, particularly for young men.
'In the last 50 years, physical strength has become less and less relevant. If you can't work in an office, you're screwed. So not only have boys lost the idea that they can grow up to have a traditional father's role, head of the household, they've also lost the notion that they can sell their physical strength. No wonder they get self-respect out of beating and knifing each other. Nobody's talking them through the process, nobody's trying to explain. That's why I lobbied the government, as we need to continue lobbying the government, for more focused skills training.'
Suddenly, I find a pile of papers thrust into my hands.
'Now, you can keep a copy of these,' says Ken. 'This is the latest from my economic adviser - I get a printout sent to me every day. It explains everything I've just been saying about the credit crunch.' As he starts to scribble down email addresses, I hear myself saying, 'This doesn't look like retirement to me.'
Ken gives me a sly little grin. 'Oh, it isn't, not really. I'll be back. I'll be back in three years. Well - nobody can say for sure, of course, but if Boris dropped dead tomorrow I'd run. I'm only 43 inside!'
Ken has no magic wand, and the British left has no supernatural backing. What we have is everything to play for, in a world waking up after a generation of deregulated markets with a shocking hangover, and what we need is the energy to forge links and create something a tiny bit better. At 63, Ken Livingstone's energy is catching. Let's hope it spreads again.
Laurie Penny is a freelance journalist who blogs regularly for the New Statesman.