The block is no more than the land and building area defined by streets. It is the nature of the interface between the two, which has a critical impact on the quality of the spaces between those buildings. The importance of the block to city life is well rehearsed, and in any case, we seldom find ourselves in the business of making cities from scratch. But we are in the business of making new houses, neighbourhoods and new local centres, and we need lots of them: 250,000 a year to be impre...