Ever since Labour published its manifesto for the snap election it became clear to me that tackling Jeremy Corbyn is going to require a bit more than simply calling him a bearded Trot. This is because some of his prominent policies, while notionally quite left wing, are actually rather popular with many natural Conservative voters. Renationalising the railways and utilities, ending the automatic contracting-out of public services – you will find plenty of support from people on the right who, while generally sceptical of state intervention, feel that the current arrangements are not a free, open market which offers consumers a genuine choice. Rather they come across as a racket designed to enrich a small band of business interests which have been good at sucking up to government ministers.

So it is with Labour’s plan, announced yesterday, to launch an English Sovereign Land Trust – a body which would be empowered to pick up land for house-building at a price which reflects its current, agricultural value rather than its development value. Predictably enough, there have been howls of outrage from landowning interests, and no wonder. There is a huge amount of money at stake. The difference between the value of rural land with and without planning permission is immense. An acre of farmland worth £10,000 can suddenly become worth £1 million at the stroke of a planner’s pen.

This isn’t a free market in operation. It is a case of the planning system creating value through an artificial shortage. The planning system deprives most landowners of the right to develop their land, depressing the value of their assets, but then pours riches into the pockets of a lucky few who are able to play the system to their advantage. It inflates house prices and is a huge recipe for corruption. We don’t know how much of it goes on, but there must be a huge temptation for landowners to offer backhanders to public officials who have it in their power to deliver that windfall.

A truly free market solution would be to abolish the planning system altogether and let anyone build what they like, wherever they like. That would mean the value of most agricultural land rising, because it would become possible to develop it, but bring about a sharp fall in the value of land with planning permission – because it would no longer come with a special privilege. The trouble is that no Conservative government is ever going to do this because it would be electoral suicide – it needs the Nimby vote.

If it is politically impossible to abolish the planning system, the Labour proposal makes perfect sense. It would still mean the value of land increasing sharply when it was picked out for development; the difference is that instead of going into private pockets it would go into the public purse, and be available for building the infrastructure needed to serve new developments – something which, at present, is partially funded by informal agreements between councils and developers, and by a development tax called the Community Infrastructure Levy.

Landowners will froth at Corbyn’s proposal but it would really just revive a system used by governments of both colours to build the post-war new towns – for which land was compulsorily purchased by development corporations. Few complain at the lack of infrastructure in Milton Keynes – the road system there contrasts hugely with congested rural lanes which have to serve many more recent developments.

Where many conservatives will differ from Jeremy Corbyn is what happens to the land once it has been bought for development. While Corbyn has in mind mass building of council properties, I would far rather see most of the land sold onto private developers and to individuals wanting to build their own home. But the principle of a sovereign land fund is sound.

There is one problem, however: many of the large housebuilding companies have extensive land investments, and there is a question of what it would do to their balance sheets if those landbanks had to be down-valued to take account of the new policy. We don’t want to cut the value of development land only to find that the companies we need to build the houses have become insolvent. For this reason, any new system might have to be phased in – say by giving developers five years to build out sites which currently have planning permission but announce from then on all large developments would be on sites which have been bought by the sovereign land trust. But it would be a huge mistake for the Conservatives to attack Corbyn’s land policy; on the contrary, they should adopt a similar policy themselves. As I wrote in my e-book, 'A Broom Cupboard of One’s Own', in 2012, the constituency of frustrated would-be house buyers is becoming larger by the year. The Tories are going to need those votes.