At the heart of Whitehall, adjacent to Downing Street, King Charles Street Quadrangle sits within the Grade I listed home of the Foreign, Commonwealth and Development Office.
For many years, the historic courtyard had primarily served a practical purpose, including vehicle parking and ceremonial use. The space also faced a number of challenges, including drainage and subsidence issues, uneven surfaces and accessibility constraints.
The redevelopment provided an opportunity to rethink the quadrangle, creating a greener, more accessible environment for staff and visitors while respecting the significance and character of its historic surroundings.
Led by landscape architects Gustafson Porter + Bowman, with Maylim Limited delivering the landscape works, the completed scheme has transformed the previously hard courtyard into a series of planted garden spaces connected by meandering paths.
Introducing established trees and planting into a historic, heavily constrained environment requires careful consideration of what is happening both above and below ground.
GreenBlue Urban supplied four RootSpace tree pits as part of the landscape works, providing uncompacted soil volume beneath the surrounding hard landscape to support long-term tree growth.
The four tree pits support Liquidambar styraciflua ‘Moraine’, positioned to frame the Downing Street archway and northern façade of the quadrangle.
In an environment where the landscape still needs to accommodate pedestrians, servicing and vehicle movements, the RootSpace system allows suitable rooting volume to be provided beneath load-bearing surfaces. This gives tree roots access to the soil, oxygen and water they need while allowing the space above to continue performing its required function.
Trees form part of a much wider transformation of the quadrangle.
The landscape has been arranged as a collection of outdoor rooms, with planting used to frame views, provide enclosure and create areas where staff and visitors can meet, relax and move through the space.
The result is a space that has retained the formality required of an important government setting while becoming considerably greener and more welcoming for everyday use.
King Charles Street Quadrangle demonstrates how significant historic settings can be adapted to meet modern expectations for accessibility, biodiversity and high-quality green space without losing their character.
The completed King Charles Street Quadrangle project was named a finalist in the Excellence in Small Landscape and Garden Design category at the 2025 Landscape Institute Awards.
Image credit: Richard Bloom.
