So there’s a guy called Stephen Jorgenson-Murray who’s contributed a dozen or so articles to these pages. Nothing unusual in that, of course – lots of people (journalists, politicos, wonks, interested nerds) do it.

But what makes Stephen unusual is that, after a while, his family started getting involved too. Last year we had a piece on Teesside from his wife Danni. And back in June we had this piece of genius from his dad John, who used graph theory to work out where the Proclaimers had walked 500 miles too.

I can think of another married couple who’ve both contributed to CityMetric, but the Jorgenson-Murrays are, thus far, the only extended family group we’ve had get involved. All of which is a long way of telling the rest of you to raise your respective games.

Anyway. The reason I say all this is because yesterday I wrote an article arguing that that too much of London was taken up by golf courses, and that maybe we should look at reusing some of them as parks or housing estates or other more useful things. But I was a bit vague on exactly how much golf course this city has, on the grounds that I didn’t actually know.

What do I find awaiting me this morning, though, but an email from Stephen:

Hi Jonn

I showed my dad your golf courses article and he worked out how much area they take up in London.

…game on. Amazing what you can do with Ordnance Survey data, isn’t it? It continues:

In Greater London, there are 131 courses (some crossing the border) covering 51.1 km² (19.7 mi²).

Within the M25, there are 189 courses covering 76.4 km² (29.5 mi²), which is 3.3 per cent of total land.

Why the first map uses the boundaries of the multi-borough constituencies used for elections to the Greater London Assembly is something I suspect we shall never know.

Anyway. I’ve not checked John’s work – I wouldn’t even know how – so can’t guarantee it’s entirely correct. But let’s work on the assumption it’s at least roughly right, and ask how many homes this land could provide for.

Well: a square kilometre is 100 hectares, so the lowest level of housing density discussed in the housing plan – 35 homes per hectare – works out to 3,500 homes per square kilometre. So: repurpose all of Greater London’s golf courses as housing, and at minimum densities you have space for (51.1 x 3,500) homes, which is 178,850.

Administrative boundaries are a bit meaningless, though, so let’s run the same calculation for all golf courses within the M25. This time the resulting figure is (76.4 x 3,500), which is 267,400.

At low densities, we’re looking at family homes rather than one-bedroom flats. So it is entirely plausible that you could provide big, comfortable homes for another 1 million people within the M25, using no land other than that currently taken up by golf courses.

We’re never actually going to do this, of course, and even if we could we probably shouldn’t: even if golf club memberships are falling, some courses will survive, and anyway open space is a good thing. But the point is clear, all the same: London is keeping a lot of land free for golf.

I remain unconvinced that, in the midst of a housing crisis, this is actually a good thing.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.

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