Last week, figures were published suggesting that Oxfordshire needs to build a staggering 100,000 houses by 2031, an increase of nearly 40 per cent in under 20 years. For Oxford, the proposed increase is 28,000 houses – the size of Didcot. This equates to roughly a 50 per cent rise in Oxford’s permanent population.

These numbers are not based on what we can sensibly accommodate without irreparably damaging our landscape or overwhelming our infrastructure and local communities. Instead they are based on ambitious plans for economic growth that have never been subject to public consultation; an unrealistic notion about how many houses developers will build in the current climate and some strange figures for population growth in Oxford city, that appear to take into account a substantial rise in student numbers even though their needs are accommodated outside of normal housing figures.

The plans would be unlikely to solve the problem of affordable housing but would certainly lead to a poorer environment for everyone.

Nonetheless, Oxford city has been quick to once again push forward its long-held ambition for expansion into the green belt.

Their plans would see development all the way to Kidlington and Begbroke, plus south of Grenoble Road all the way to the Baldons and possibly beyond.

Yet a rather surprising knight on a white charger may be riding to our rescue. Nick Boles, the planning minister who has ploughed furrows through many of the planning rules which protected the countryside, said something extraordinary last week.

In an address to Parliament he confirmed that green belts must be protected, and that building on them was not an acceptable way of satisfying housing needs. Specifically, that “unmet housing need is unlikely to outweigh harm to the green belt and other harm to constitute very special circumstances justifying inappropriate development”.

He also clarified that the “duty to co-operate” which was placed on councils in the 2012 National Planning Policy Framework did not mean that one council had to accept another’s demands, but only to consider them.

At a stroke he has undermined the whole strategy of Bob Price, the expansionist leader of Oxford City Council, which seeks to compel the surrounding authorities to let the city grow out over the surrounding green belt.

Why is the minister right to save the green belt from the city council and why is Bob Price wrong to wish to concrete it over?

It is the green belts that have preserved the character of our island, and particularly its crowded South East corner.

Green belts were created specifically to prevent the urban sprawl and ribbon development that has so damaged the environment elsewhere. The significant word was not “green”, although they tended to be mainly countryside, but “belt”.

The essence is its permanence. You cannot contain urban sprawl if you keep loosening the belt every time Oxford feels like sprawling.

What’s more, an immovable green belt is of immense benefit to Oxford and Oxfordshire even though Mr Price chooses to ignore it.

In protecting the surrounding countryside and villages it gives city dwellers easy access to the countryside. It protects surrounding towns like Abingdon being swallowed up into a Greater Oxford and it provides the environment which attracts the high end entrepreneurs we need to the county.

The medieval centre of Oxford itself is incapable of satisfactorily supporting a larger city and the tourist income which is so important relies on the city’s setting which the green belt protects.

It protects Oxford from its own city council. That alone is enough to make it essential to preserve it, as the planning minister says we must.

Of course the houses we really need have to be built, even the incredibly large numbers now suggested, if they can be justified. But we are a long way from seeing the evidence for this and they won’t be built at the expense of the green belt, as “urban extensions” of Oxford, as the city council seeks to do.