Opened in 2017, The Postal Museum at Calthorpe House provides a new home for its extensive archives and showcase for British postal history, including the transformation of the disused Mail Rail tunnels and platforms at Mount Pleasant into a visitor attraction. Following a series of optioneering studies across a number of sites, M3 was engaged to consolidate the brief and manage the design team to obtain planning and deliver the redevelopment and extension of the former Royal Mail administrative building, including the move of existing facilities.