Fraser Bond are the leading lettings and property management agents for Welbeck House - London W1T. Welbeck House is a new office development in Marylebone, London W1. Adjacent to Grade I listed All Saints Church. 2017 December - Westminster City Council decides to grant planning permission for: Demolition of existing building and excavation at basement level, and redevelopment to provide a new building comprising basement, ground and four upper floors, with retail (Class A1) use at part ground floor and part basement level and office use (Class B1) at part ground floor and part basement and.