Diplomatic service.

Through careful siting and inventive use of local materials, the new British High Commission in Nairobi is able to take advantage of passive environmental control strategies, providing a model for responsive, tropical architecture that learns from the past with integrity and never descends to pastiche.

Traversing a hillside on the edge of Nairobi, the new British High Commission is set discreetly apart from the intensity and bustle of the sprawling Kenyah capital. Designed by London-based architects Hugh Cullum and Richard Nightingale, the building is divided into two wings flanking an open columned portico that frames and overlooks the city. The view encompasses Amyas Connell's Parliament Buildings (dating from 1952 with a later neo-Corbusian phase added in 1963). Connell's crisp, tropical Modernism, which attempted to crystallise the cultural complexity of East Africa without recourse to pastiche, is a clear antecedent for Cullum and Nightingale's new High Commission. The component wings are set back from the road, creating a formal entrance courtyard on the main Upper Hill Road frontage. To the rear of the compound is a lush, steeply sloping garden, dominated by an imposing wild fig tree (the fig tree or mugumo is sacred to the Kikuyu people).Residential accommodation and a staff clubhouse are contained in small pavilions within the garden. By exploiting the height difference across the site, the integration of built form with nature is skilfully accomplished.

The portico is the building's organisational fulcrum. On the south-east side are more political and formal spaces, such as the High Commissioner's offices and a large reception area. The reception hall connects with a staircase leading up to a large glazed landing with views of Nairobi framed by the abundant branches of the fig tree.

On the north-west side of the portico are the overseas commercial aid and development sections. These are simple cellular offices arranged along a corridor punctuated periodically to admit light and provide views over the garden. This part of the building also contains an oval meeting room, sculpturally extruded from the external wall plane, and an exhibition space next to the portico. A further function of the High Commission is the quotidian business of issuing visas. The consular section is isolated in a low wing at the front of the building, topped by a curved, oversailing roof. Clerestory glazing creates the impression of the roof hovering over the consular hall.

Using local materials such as Kenyan stone to emphasise the scale and solidity of the elevations, the building embodies an appropriately modern institutional character. The dense grey stone, which closely resembles granite, is volcanic in origin. Drawing on an established tradition of local stonemasonry, the stones are undercut to give a mortarless, fine joint, so that the surface is enlivened by the slight unevenness of the hand dressing and the colour variation of individual stones.

The thermal mass of the stone walls plays a key part in the building's passive environmental control strategy. Although Nairobi lies virtually on the Equator, its high altitude means that its climate is less extreme than might be imagined. Wherever possible, the building exploits passive environmental control systems (also prompted in part by Nairobi's frequent power cuts). The siting of the building is a response to solar orientation. When the sun is low, it falls on the relatively small and blank east and west ends of the block. Generally, the building is designed to use natural cross-ventilation, with outdoor ventilation panels to the offices and fully opening windows controlled by users. The giant order of the fenestration gives rise to very deep reveals, which powerfully articulate the elevations. These provide solar shading and depth to allow additional metal baffles within the window design. As a highly functional yet dignified expression of national identity, Cullum and Nightingale's High Commission continues a tradition of responsive tropical Modernism.

Client Overseas Estates Department, UK Foreign and Commonwealth Office

Architect Cullum and Nightingale

Project team Hugh Cullum, Richard Nightingale, Nicholas Warner, Neil Fletcher, Carolyn Steel

Executive architect Hughes and Polkinghorne

Quantity surveyor D. G. Jones and Partners

Structural and services engineers Howard Humphries

Interior design and furniture Management Change Ltd.

Commissioned artist Kate Whiteford

Main contractor Mulji Devraj and Brothers

Project management G.T.M.S.

Photographs Peter Cook/VIEW