Owing to the complexity of the railway system, introducing new technologies or upgrading existing systems requires a whole system approach, ensuring effective integration and alignment with business needs. Enterprise architecture has been used to address this complexity, but there are currently no standardised enterprise architecture frameworks for the railway. The authors define an approach for building a whole railway system architecture framework by identifying architectural needs, analysing existing frameworks, and developing a proposed solution. The case study to support this work, taken from the GB Digital Railway programme, is an application of the proposed solution for producing requirements.