If I did, though, I imagine I would clear the room just as quickly as I ever did, because it’s impossible to address our national shortage of housing without addressing the worthy-but-dull issue that lies at its root: land, or, more specifically, the lack of it. There is no piece of blue-sky thinking, no big idea, that could help solve the housing crisis without explaining where we’re going to put those extra homes.

It’s thus hard to come up with a fantasy housing policy that doesn’t shatter on contact with matters of concrete (sorry) reality. Proposals that don’t even try to address the land question ascend rapidly into the realm of science fiction, whether that means Star Trek (“What if new transport technology meant we didn’t need to live near the office any more?”) or Logan’s Run (“If only there weren’t quite so many people, somehow …”).

So, let’s limit ourselves to policies that are difficult thanks merely to politics, rather than the laws of physics. Let’s imagine we had a government that was genuinely determined to solve the housing crisis. What would it actually do?

Well, it would begin by accepting that the private housebuilders were never going to solve this problem for us. The amount firms pay for land is based on the price they’ll be able to sell homes for. They’re never going to build homes at a rate that could make prices fall, for the very good reason that they’d all go bust if they did.

And so, a government set on a real solution to the housing crisis would abandon ministers’ touching faith in the power of markets. Instead, it would invest in a huge increase in social housing, loaning money to housing associations, to get them building, and allowing councils to borrow money and build homes on their patch once again. This would require a change in attitudes towards public debt, and an understanding that council housing was a long-term investment – an asset, rather than a slightly embarrassing relic of a bygone age.

This doesn’t, however, solve the question of where we’re going to put all these new houses. The standard answer to that is “brownfield” – conveniently vacant land that’s already been built on, and so won’t offend too many people if it’s built on again. But the truth is that, in much of the country, there isn’t enough of that to go round. If we’re actually going to meet demand for new homes, we have only two options: we can either build up, or build out.

Building up doesn’t necessarily mean skyscrapers. British cities, with their reliance on semi-detached homes occupying individual plots, are actually very low-density compared to most European cities. Gradually filling London with apartment blocks of the sort that line the boulevards of Paris or Vienna could go some way to meeting the city’s housing need, without turning it into the set of Blade Runner. The public sector even owns large tracts of land where we could put these new homes.

The drawback? Most of that land is occupied by homes already, in the form of existing council estates. Real world governments have shown themselves more than willing to redevelop those – but they’ve generally tried to do so on the cheap, maximising the number of private homes available at the expense of social homes, and repeatedly breaking promises to tenants.

Our fantasy government wouldn’t pull these tricks: it would guarantee social tenants’ rights to homes of equivalent size in the same area, and it would act in a way that showed that it understood these are homes, rather than simply government property for it to dispose of as it wishes. Nonetheless, it would replace some of the more crumbling and impermeable postwar council estates with new streets, filled with European-style mansion blocks rather than the cramped, magnolia, hall of residence-style that characterises most British new-builds. Such is the need for new homes that, in select areas, it would probably use stronger compulsory purchase rules to acquire land.

Increasing density in this way would allow it to increase the number of both private and social homes, creating vibrant, new mixed communities. This would probably take a bit more cash upfront than past redevelopments – but since our government has shown itself willing to invest for the long-term, this shouldn’t be a problem.

Comprehensively redeveloping the inner cities will take time – but luckily, there is an easier way to meet housing need. All around London, Oxford, Bristol and other cities in housing crisis, there is open space, often inaccessible to the public and occupied by nothing prettier than some chemical-drenched arable land. The reason we don’t build on it? Because when green belts were introduced in the mid-20th century, it just happened to be unoccupied.

Our fantasy government would recognise that a land-use policy designed for 1955 was not much use in 2017. It would take its inspiration from Copenhagen, whose “fingerplanen” has seen development take place in five rail corridors (the “fingers”) extending outwards from the city, separated by green space.

Is it time to rethink Britain’s green belt?

To that end, the government would formally review the green belt to identify areas that would be better used as the site of new communities. Around London, it would prioritise areas next to railway lines, such as that baffling open space surrounding much of the eastern end of the Central line. In smaller cities such as Oxford, it would designate new urban extensions, linked to the city centre by new tram lines. Further green belt land would be turned into public parks: surely an improvement on the inaccessible farmland that sits there now. And, to minimise public whingeing, it could even designate new green belt, to protect land in areas less plagued by demand for housing.