Build-to-Rent (BTR) developments have expanded rapidly in the UK since 2013, often advertised as providing better quality rented accommodation for university-educated Millennials than available elsewhere in the private rental sector. However, the implications of this type of housing development, and especially its affordability, are poorly understood at the city scale, partly due to a lack of evidence of where these developments cluster and what they add to the housing stock in terms of property type, amenities and cost. This article draws on data relating to 373 BTR developments in London (representing over 40,000 housing units) to show that developments are clustered where transport-related infrastructural investments have opened ‘rent gaps’ that can be exploited by developers. Exploring how these BTR schemes are marketed, the article shows that this accommodation is typically provided through new short-term ‘subscription services’ which allow developers to rent property at a premium. Questioning whether BTRs really add affordable ‘local’ homes to the city, the article concludes that BTR provides ‘quick-fix’ rental accommodation which is doing little to solve London’s housing crisis. We focus on the London BTR market and how the expansion of this housing type is reshaping the sociospatial geographies of the city.