What would the world look like if Kevin McCloud had his way? What if each of us had the chance to build our very own Grand Design, letting our streets be lined with personal visions, liberated from the identikit brick boxes offered by the usual big housebuilders?

A glimpse of this world exists, sort of, on the outskirts of Bicester in Oxfordshire, where the country’s biggest self-build experiment has been under way for 10 years. Graven Hill is a place where rooftops tilt, zigzag and bulge, where windows come in circles, squares and triangles, or poke out from unexpected places. There are balconies fashioned from glass, steel and rustic timber clinging to facades of stone, brick, wood and render, along with every type of fibre-cement board available. Wandering the freshly tarmacked streets feels like walking through a building supplies catalogue. Panels of fake wood are proudly fixed next to rusted cor-ten steel and bits of slate, as if residents were fed fizzy drinks and let loose in a cladding warehouse.