Want to know something funny? Not “ha ha” funny, more funny in the sense that “this could very possibly ruin your life”. According to analysis published by Shelter today, there are just 43 homes left in the whole of Greater London that are still affordable to the average first-time buyer. My sides.

The housing charity looked at the salaries of people in different regions, worked out the amount banks would currently lend them, then compared those figures to the current cost of a family home. In regions such as the north-east, where just 42% of homes are now affordable, its findings are mildly worrying.

In London, though, they’re catastrophic: just 0.1% of homes with two bedrooms or more are now affordable to the average first-time buyer. In other words, if you’re a Londoner who doesn’t own a home, and doesn’t have parents who are willing and able to bung them, say, £30,000, then it’s probably time to come up with an ambition more attainable than “suburban normality”.

Developers bend over backwards to get out of legal obligations to include affordable housing

There’s a very obvious reason why this situation has arisen: London simply doesn’t have enough homes. The number of people who live here has increased by nearly a fifth in just 15 years; the number of homes to put them in hasn’t. And so, prices have spiralled. It’s tempting, not to mention satisfying, to blame all this on the property developers who are doing the building, and who bend over backwards to get out of legal obligations to include affordable housing in those blocks they do bother to throw up. Even that phrase, “affordable housing”, has acquired a baffling new definition, in which it can mean as much as £2,800 a month.

But developers only operate within the context government sets for them. The new definition of affordability was handed down from on high, and means “up to 80% of market rents”. In other words, if we didn’t have a housing crisis to drive rents skyward, affordable would just mean “affordable”.

There’s another way in which developers are responding to government policy. There’s a close relationship between the price of homes and the price of land in the places people might want homes. The house price boom means you can sell new homes at higher prices; but it means you’ll pay higher prices to buy the land to put them on, too. This is a very big reason why London isn’t building enough houses – and why those we do build are disproportionately likely to be luxury flats in riverside skyscrapers. Building in London is an expensive business. Unless something happens to change that, building genuinely, rather than officially, affordable homes for buyers who aren’t investment bankers simply isn’t profitable enough to get developers interested.

So if this mess is not entirely the developers fault, then whose fault is it? One popular option is the British government. Over a period of decades it’s made it harder for councils to build homes, introduced planning rules which limit what and where you can build, and let developers themselves off the hook. What’s more, there’s an argument that, if the private sector won’t build the homes we need, the state itself has to: that the only way out of the crisis is a major government-funded building programme. If any political party has a plan for making this happen, it forgot to offer the details in its manifesto.

But there’s another possible culprit too: us. We the people campaign against skyscrapers. We campaign against mythical threats to London’s sacred green belt, even though more land in Surrey is given over to golf courses than to housing. We want house prices to come down, but we don’t want to do any of the things that might make that happen. Many homeowners don’t even want that. The reason politicians haven’t addressed the housing crisis is because many of us don’t want them to. Keep an eye in those last 43 affordable homes, though. Now that everyone knows about them, they’ll be gone before you know it.