Everyone knows that high streets are under threat, caught in spirals of decline driven by the rise of online shopping. It’s also obvious, or should be, that the government’s big idea for responding to this crisis, which is to make it possible to convert shops into homes without planning permission, mostly makes things worse. Welcoming shop fronts get replaced by crude brick walls with sash windows punched into them. Dead space is created on the frontage; footfall slackens. The high values of residential property give owners a strong incentive to close shops and make them into cheap flats – cheap to build, that is, not to buy or rent. Costa’s Barbers, a project in Battersea, south London, shows how such changes may be done differently. It’s a shop-to-home conversion, except that its design does everything it can to animate the street where it stands, and to leave open the possibility that future uses will involve transactions between inside and out. It’s a work of craft and delight that at the very least brightens its surroundings. …