Sustainable construction attempts to mitigate the destructive impacts of building on the global environment. Mega‐projects in London, such as Blackfriars Station and the Shard, symbolise urban renewal and are promoted as engines for sustainable development, principally through their use of sustainably procured materials. Unique buildings which are monumental and often state backed act as niches or incubators for sustainable construction, because they operate as protected spaces where the general rules of construction do not apply. Decision making in sustainable construction is complicated by the multiple state and public stakeholders involved in projects such as large stations and skyscrapers, and the different perspectives of architects, developers, procurement specialists, end users and others. While there are diverse actors involved, there has been some international convergence in the construction sector around how to deliver sustainability, and sustainable procurement has become the primary social and technological change through which more sustainable approaches to construction are delivered. Using interviews and questionnaires undertaken with six leading contractors involved in some of London's mega property and transport infrastructure projects, we analyse how sustainability procurement is deployed in the construction industry. Socio‐technical transition theory provides a way to understand the context‐specific developments led through mega‐projects, which are at the forefront of promoting the use of sustainably procured materials and technologies. Our research demonstrates that moves to deploy a more sustainable approach are based around modifications to current practices rather than fundamental transformation. Cost and risks are frequently cited as barriers to the sustainable procurement of materials, while some contractors are sceptical of the improvements that can be delivered through sustainable procurement.