Without a doubt, Canada scored Commonwealth gold when it secured a Greek Revival pile on a prime corner of Trafalgar Square for its High Commission. Flying the maple leaf in the heart of London is advertising you couldn’t buy today; particularly a (politically) small country that does big business in the capital.

Over a century, though the Grade II-listed building became a warren of unsympathetic conversions and cheap carpeting – fine for the parade of flag-embroidered backpackers replacing lost passports, but not much else. When the government sold the High Commissioner’s residence and chancery on Grosvenor Square last year for £306 million, it funnelled some of the earnings into a ground-up renovation of Canada House, joining it to the neoclassical building next door on Cockspur Street to create an 8,000 sq m cultural and diplomatic headquarters. Where the two buildings meet is a new top-lit atrium over a cascading staircase and a feature wall of Canadian hemlock. Welcome to the Great White North.

The architecture practice Stantec, with offices in London and Canada, led the project with heritage architects Purcell, sourcing every hand-crafted furnishing, artwork and piece of cabinetry from the mother country. The new square-facing entrance opens to a broad, vaulted foyer laid with Canadian red oak, decorated with Brent Comber’s cedar-block tables and hung with a light installation by Vancouver lighting company Bocci, designed with amorphous blown-glass ‘57’ chandelier.

Elaborate wool carpets in every room – 13 rooms are named after Canada’s provinces and territories and four after seminal Prime Ministers – were custom-tufted after paintings selected through a cross-country competition. Themes of light, climate and geography are reflected in the icy blues and vivid harvest reds of the wool.

Two years and some £10 million later, the interior holds its own among London’s finest and most fashionable interiors, yet it is resoundingly Canadian. Not in a rah-rah way, but subtly, as is our wont.