London is wonderful metropolis but those that live and work in the city know that it is really the congregation of many different fiefdoms. Each place abides by its own rules and cherishes its own identity. There is no such things as a Londoner; people identify with their local community, as well as the physical context and history of their surroundings. This brand of fierce localism has a knock-on effect for architecture and planning but what happens to the places that fall between the gaps? Boroughs care less about the impact of something they build on their neighbour. Also, borders provide uncertainty about responsibility for particular areas and the populations that live there. Boundaries can therefore give rise to neglected landscapes but they also provide huge opportunities for innovation and experimentation. The Boundary Estate changed social housing for generations, can we use hidden hinterlands to create a better city?