1 Marylebone High Street
The transformative reuse of a 1940s building as a high-performance, low-carbon workplace—retaining the structure, enhancing biodiversity, and integrating a rooftop pavilion to support long-term adaptability in the heart of Marylebone.
Project Details
Type
Mixed Use (Office Led)
Location
City of Westminster, London
Client
The Howard de Walden Estate
Value
£10m
Collaborators
Structure
Fairhurst
Building Services
KJ Tait
Team
Jonathan Holt
Rasha Kamhieh
Adam Szyman
Pooja Patel
Thidaa Roberts
Federico Pruneti
Lisa Ames
Photography
n/a
Located at the junction of Marylebone High Street and Marylebone Lane, this project reimagines a 1940s corner building within the Harley Street Conservation Area as a best-in-class sustainable workplace. The proposals retain and adapt the existing fabric while upgrading the building to meet contemporary standards of energy performance, accessibility and occupant wellbeing.
A series of sensitive interventions include a reconfigured and more welcoming entrance, extensions to the rear and roof, and the creation of a rooftop pavilion and garden. These additions intensify the building’s use, improve its clarity and legibility in the townscape, and introduce a layer of green amenity into the dense urban setting.
The project adopts a rigorous fabric-first approach. The majority of the original structure is retained—preserving embodied carbon and avoiding unnecessary waste. New extensions are lightweight and designed for disassembly. All services will be upgraded to all-electric systems, targeting an operational energy use of 91 kWh/m²/yr—equating to a 58% reduction from existing levels.
Alongside this, the scheme enhances biodiversity and user experience through generous planting, biophilic design, and improved end-of-trip facilities. The result is a characterful, high-performing retrofit that reflects the Estate’s commitment to long-term stewardship and net zero carbon by 2040.
