Like ‘sustainability’, ‘flexibility’ is one of those words we use very lightly but usually manage to avoid building into our designs on the grounds that it costs too much, is too long term and doesn’t sell as an idea. Past attempts to incorporate flexibility into the planning of new homes have almost always resulted in uneconomical solutions. In the early 1970s at least one scheme of experimental flexible housing was built in London using a system developed by the Danish architect N. John Habraken: this permitted dwellings to be subdivided, adjoining dwellings to be combined, enlarged or reduced, or subdivisions within dwellings to be altered. The fact that this was an experiment that has not been repeated speaks for itself although, as a social-housing scheme built by the soon to be defunct GLC, there was unlikely to be much demand for the type of change that the system allowed.