When I lived in Bradford I sometimes used to gatecrash the student tours of the town led by the late social historian Jack Reynolds. He knew everything about the history of Bradford, and how it was reflected in the city's architecture. It was a pleasure to hear him.
One of the points he touched on was how the design of mill buildings changed with the advent of the Luddites and machine-wreckers of the early nineteenth century. Barkerend Mill, he pointed out, was built with high walls and a gateway like a fortress. It was designed to be defensible.
I thought about that while visiting a friend on the weekend. She lives on a 1960s estate. The main road through the estate has houses on both sides, all facing the road and with no walls or fences betwen them and the pavement. So were all houses built from earliest times up to very recently. It was the most convenient situation - facing the road - and there was no reason not to build that way.
Drive round a modern estate - say one built in the last ten or fifteen years. The design will be - one or two (usually one) main roads through, with cul-de-sacs off on either side. Smaller cul-de-sacs come off these. No houses face the road - instead high fences or walls hide the backs of the houses, each one of which now faces onto its own small cul-de-sac.
These too are built to be defensible. Not against mobs bearing hammers, but against groups of youths congregating outside one's house (in a particularly grim 60s estate in Gloucester I recently saw about 30 youths sitting in someone's front garden). They are built to encourage only the people who live on a street to be there. The roads and pavements of these cul-de-sacs are quasi-private places, gated communities without gates.
Meanwhile the few remaining public spaces on such an estate - the square of park, the small green with its chippy, shop and launderette, become the danger zones - the places of graffiti, broken glass, wire mesh on the "offy" window.
A location near a public park was for most of the twentieth century a selling point for an estate agent. Now it's a drawback. It would be interesting to know at what point this change - and the change in estate design - occurred. I reckon the late 80s/early 90s won't be too far out.