David and Anjana Devoy's tiny coach house was proving too small for them and their two children. So they decided to build a new house in their own garden, which was big by London standards. But this particular grassy plot came with problems. It was overlooked by huge blocks of flats, and in the middle of it stood a chestnut tree they weren't allowed to cut down. They came up with an inspired solution: they would build a curving house along the borders of their plot. What's more, they would do a lot of the work themselves.