Yes, in that sense the logic of the Lib Dem leader is sound. It is just that he wants to build them in the wrong place. There is no need to impose a series of new cities on the lush fields of the South East. It is far too early to start a war – and it will be a vicious and protracted war – with the green-wellied Swampies of the Home Counties.

Nick Clegg should have a look at the London Plan – which I bet he hasn’t even read – and the further alterations that we have announced this week. He will find a massive 1,000-page vision for addressing the housing shortage. It means accelerating the creation of affordable housing in the capital – on top of the record numbers built in the past six years, under this mayoralty.

The plan is for far more homes for private rent and part-buy-part-rent. It means systematically making public land available for development. And it means making better use of the brownfield sites across the city to deliver, in all, about 47,000 new homes per year.

That is a huge number – more than has ever been delivered before – and reflects the scale of the demand. Much of the UK’s population growth can be attributed to the dynamism of London, where we have a combination of ever-growing life expectancy (there is a ward on the Harrow Road where people are now living, on average, to 97.1) and more live births.

And yet this demand for London housing is not unprecedented. What few people realise is that the population of the city is still several hundred thousand lower than it was in 1939, before the Blitz. It is barely bigger now than it was in 1911. There are still huge areas of Greater London that could take more housing; and indeed, some areas that at one time used to have more housing.

There are at least 33 brownfield opportunity areas in London, and many of them are, of course, to the east – scene of the post-industrial decline that followed the loss of the docks and much manufacturing industry. There are abandoned factory sites, old docklands, acres of scrub and buddleia waiting to be regenerated and turned into beautiful homes. Many of these places are in the hands of the public sector.

These sites have stood idle for decades, because the economic case for commercial development was never good enough. The potential value of the homes was never high enough – because people need money to help pay for a home, and there wasn’t the money because there weren’t any jobs. Well, that is changing now: London is to some extent being literally re‑orientated, as investment floods in to the old docks, and as new jobs are created.

But there is still a huge zone of post-industrial land that has proved impossible to shift and where development has never been viable – and that area would be transformed, of course, by the addition of one obvious motor of economic growth: a new airport and logistics hub in the estuary. At a stroke you would transform the economics of building on the brownfield sites of the Thames Gateway. You would create a 24-hour airport that would finally enable the greatest city on earth to compete properly with our rivals. You would end the aircraft noise misery of London and other environmental problems. You would turn the east of London into an economic dynamo – as it once was – and no, you would not decimate the economy of west London. That is utter nonsense.

West London has always been one of the most prosperous parts of Europe, and was long before Heathrow, or air travel, were even dreamt of. If anything, you would relieve that part of London of some of the congestion and rent gouging that is making life difficult for so many businesses. You would also release a suburban area now occupied by an airport – and you would have space to accommodate 200,000 people, as well as university campuses and hi-tech industry. You already have four Tube stations and Crossrail, as well as the Heathrow Express. It is a superb location, and would be snapped up by the market.

That is where you build the garden city, with an Aerotropolis on the brownfield sites to the east. You would have regeneration in east and west; you would solve the housing crisis. You would not have to build a series of Cleggsvilles and Cleggminsters all over the South East. Why don’t we just get on and do it? One day, having exhausted the alternatives, we will.