Mike Russum.

The role of the diagram is key to the development of designs within our office. Our work is developed through key design stages by hand drawing-which we can comfortably prepare quickly to cuttingly reveal the nub of the issue. We commence a design by preparing a range of sketch solutions and appraise these to pursue single options, or as is more probable hybrid solutions that embrace a number of the positive ideas. Generally a concept sketch/diagram emerges as the distillation of our objectives for the design. If the concept sketch is robust it becomes a touchstone for the design development. At a detail level we develop supporting drawings that explore and inform the design development and detail enrichment of the project.

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This is evident in our diagram for the car park at Chichester (right). Two further drawings accompany the concept sketch showing the development against the 'touchstone' diagram. The diagram works at different levels. At an urban level, by representing the historic layout of Chichester and the arrival of rail infrastructure. It also sets out our 'humane' aspiration, segregating pedestrians from the car circulation pattern. The diagram and hence the building weaves these aspects together into a holistic proposition. The diagram sets out the existing condition: Chichester's Roman town plan-a fortified city with North, South, East and West Gates linked by axial streets; the Cathedral; the 'leakage' and erosion caused by the arrival of the railway through the South Gate; and the new dual carriageway.

The red overlay (above) then reveals the intention of the project: a new city wall extending from the rail infrastructure to screen the car park, straddling the dual carriageway and meeting the original city wall; the re-establishment of the clarity of Chichester as a city contained by walls; a new west city entrance; and the pedestrian route reinforcing the purpose of the new city wall. MIKE RUSSUM, BIRDS PORTCHMOUTH RUSSUM

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Admired: Of the many brilliant diagrams sketched by Jim Stirling, the diagram we would cite is his concept sketch during the competition project for the Wallraf-Richartz Museum in Cologne in 1975 (right). The sketch is volumetric but not of a 'building' but instead circulation space. The diagram illustrates a series of intriguing interlocked foyer spaces that shift off axis in a progressive dynamic arrangement. The composition is asymmetric yet beautifully balanced, the programmatically driven dynamic foyers contrasting with the stillness of the 'cathedral void'. The diagram's potency is heightened by the presence of the ghostly 'cathedral void'.