Over the past 12 months, the issue of privatisation has surged back into the news and the public consciousness in Britain. Driven by mounting concerns about profiteering and mismanagement at privatised enterprises, Jeremy Corbyn’s Labour party has made the renationalisation of key utilities and the railways a central plank of its agenda for a future Labour administration. And then, of course, there is Carillion, a stark, rotting symbol of everything that has gone wrong with the privatisation of local public services, and which has prompted Corbyn’s recent call for a rebirth of municipal socialism.

Yet in all the proliferating discussion about the rights and wrongs of the history of privatisation in Britain – both from those determined to row back against the neoliberal tide and those convinced that renationalisation is the wrong answer – Britain’s biggest privatisation of all never merits a mention. This is partly because so few people are aware that it has even taken place, and partly because it has never been properly studied. What is this mega-privatisation? The privatisation of land.

Some activists have hinted at it. Last October, for instance, the New Economics Foundation (NEF), a progressive thinktank, called in this newspaper for the government to stop selling public land. But the NEF’s is solely a present-day story, picturing land privatisation as a new phenomenon. It gives no sense of the fact that this has been occurring on a massive scale for fully 39 years, since the day that Margaret Thatcher entered Downing Street. During that period, all types of public land have been targeted, held by local and central government alike. And while disposals have generally been heaviest under Tory and Tory-led administrations, they definitely did not abate under New Labour; indeed the NHS estate, in particular, was ravaged during the Blair years.

All told, around 2 million hectares of public land have been privatised during the past four decades. This amounts to an eye-watering 10% of the entire British land mass, and about half of all the land that was owned by public bodies when Thatcher assumed power. How much is the land that has been privatised in Britain worth? It is impossible to say for sure. But my conservative estimate, explained in my forthcoming book on this historic privatisation, called The New Enclosure, is somewhere in the region of £400bn in today’s prices. This dwarfs the value of all of Britain’s other, better known, and often bitterly contested, privatisations.

Since 1979, half of the UK’s publicly owned land – 2 million hectares – has been sold to private interests. Photograph: Alamy

It is difficult to overstate the significance of this colossal land privatisation, and the manifold damages to the social and economic fabric of the nation that have been caused. Those damages – which my book surveys at length – are apparent especially in relation to the other issue currently on everyone’s minds in Britain alongside privatisation – housing, and the nation’s acute housing crisis. Selling public land to private-sector developers, who have long been the biggest buyers of government land, was supposed to have helped alleviate Britain’s housing problems, but it has done nothing of the sort.

To begin to see why, consider three of the biggest housing stories of recent weeks – the housing secretary Sajid Javid’s threat to developers to “use or lose” land with planning permission sitting in their land banks; Labour’s plans to enable local authorities to acquire private land at existing-use value to reduce the cost of council house building, and the decision by Labour’s national executive committee to call on Haringey council to rethink its controversial Haringey Development Vehicle (HDV). For although one would not know it from media commentary, all three are in large part land-privatisation stories. Developers’ bulging land banks are chock-full of land acquired from public bodies, on which they could have built new homes, but have chosen not to. Local authorities are only in the perverse position now of needing enhanced powers to affordably acquire land for a new generation of council houses because, for four decades, they have been forced to sell the land needed to build on. Local opposition to the HDV was rooted in the fact that it would see significant amounts of valuable public land transferred into a joint venture between the council and its development partner, Lendlease, with concerns about how many of the homes built by the HDV in the place of existing council estates would be available for social rent.

If today the government could take one single action that would do more than any other to help arrest the intensification of Britain’s housing crisis, halting the sale of public land would be it. To be sure, with half of Britain’s valuable public land having gone, much of the damage has already been done – it would be difficult, not to mention politically highly controversial, to get much of that land back. But if half has gone, half is still left. This land should be protected, treasured, and used for public benefit, before it is too late.

• Brett Christophers is professor in the Department of Social and Economic Geography, Uppsala university. His book, The New Enclosure: The Appropriation of Public Land in Neoliberal Britain, will be published in autumn 2018