25 September 2025
The Portman Estate welcomes latest business to One Great Cumberland Place, as this flagship West End office development approaches full occupancy
- Sustainable Development Capital LLP (SDCL) arrives on the sixth floor.
- The final office floor is also now under offer. Full occupancy should be achieved shortly.
Photo credit: Dirk Lindler
The Portman Estate today announces the arrival of Sustainable Development Capital LLP (SDCL) to One Great Cumberland Place, its flagship development in the heart of the West End. With the fifth floor also under offer, the building will soon reach full occupancy; a milestone for one of central London’s most sought-after office schemes.
Adjacent to Marble Arch and Hyde Park, One Great Cumberland Place exemplifies The Portman Estate’s forward-thinking approach to placemaking, sustainability and hybrid working.
Chris Dunlop, Director – Head of Commercial Property at The Portman Estate, comments: “We’re very happy to welcome SDCL to the sixth floor of One Great Cumberland Place. Having relocated our own headquarters onto the fourth floor earlier this year, SDCL joining us in the building further showcases the continued demand for offices that prioritise sustainability, flexibility and wellbeing.”
Founded in 2007, SDCL is a specialist energy efficiency developer and investor that has pioneered the financing, development, construction and management of energy efficiency, on-site generation and energy infrastructure projects across various sectors. Jonathan Maxwell, CEO of SDCL, said: “We’re excited to move into a building in the heart of Marylebone, which is a great place for us to continue our growth as experts in the energy sector. We look forward to welcoming our clients into this new space.”
SDCL joins a curated mix of occupiers including Adams Street Partners and Moco Museum London, which recently celebrated its first year in London and houses a unique collection of over 100 modern, contemporary, digital and immersive works at 1 Marble Arch. x+why manage the day-to-day running of flexible workspaces on the second and third floors, the reception lobby and the eighth floor, a unique members’ clubspace known as The Orchard.
Designed by AHMM, One Great Cumberland Place spans 59,331 sq ft and features green roofs, heat recovery systems and photovoltaic panels, all behind a retained Art Deco facade. The building is certified BREEAM ‘Excellent’, placing sustainability at its core.
The Portman Estate relocated its headquarters to the 1920s building earlier this year, occupying 8,400 sq ft of bespoke office space, designed in collaboration with Gort Scott. The Estate’s office fit-out was shaped by employee consultation and the layout preserves expansive views of Hyde Park through careful placement of new rooms and the use of curved corners. Sustainable materials and planting were central to the design, with a cafe–style workspace at the heart of the floor, featuring generous greenery and a focal tree.
The Portman Estate’s 110-acre portfolio continues to evolve with developments like One Great Cumberland Place, responding to changing occupier demands and supporting a thriving mixed-use community in Marylebone.
