Spanish guile.

The design of new offices for a firm of lawyers in the southern Spanish city of Cadiz proclaims the virtues of elegant restraint, use of few materials, and manipulation of marvellous south light.

The city of Cadiz is said to have been founded in the eleventh century BC by the Phoenicians. An ancient maritime port and naval base, strategically placed to the north of the Straits of Gibraltar, it has inevitably had a turbulent history; but with fine streets and squares it has long been considered one of the country's most beautiful cities. Built upon a small peninsula on the south side of the Bay of Cadiz, and drenched in Atlantic luminance, it is called the city of light.

In designing new offices for a firm of lawyers in the city's Bahia Blanca district, the young Cadiz architect, Tomas Carranza, began with the idea of trapping and manipulating this extraordinary light, so that it becomes both a physical source of pleasure and metaphor for enlightenment. His approach, which weaves pure form, a few materials and light into poetic symphony, suggests affinity with another compatriot, Alberto Campo Baeza.

Inserted into the first floor of a residential block, the offices were originally two apartments which were separated by the building's service core. Though of different sizes, they were arranged in broadly similar fashion with a maze of intersecting rooms either side of a corridor. When knocked together the space became an uneven rectangle running from west to east and measuring approximately 35m long and 11m wide. The long axis is marked by a row of loadbearing columns.

The brief asked for a main office and meeting room, eight private offices, clients' waiting room and reception, boardroom, library, kitchen and lavatories. Since it was not possible to alter the existing rhythm of windows in perimeter walls, Carranza had to work within it, altering the pattern of dividing walls and establishing one central corridor down the long axis. In general, rooms get smaller as you move west, away from the great curving corner with its big windows on the north-east. Offices on the north side overlook the street, on the south, an inner courtyard. A new entrance opposite the lift leads to a waiting room and reception.

Such a description gives no clue to the elegant sobriety with which this scheme has been executed. Wood is the principal unifying material, with oak being used for Carranza's range of restrained office furniture (desks, bookcases), floors, panelling and internal window frames. The richness of the material is underscored by use of pale travertine marble and white plaster on walls.

The hollow south wall of the corridor, 400mm in depth, accommodates boardroom bookshelves, archives and pantry cupboards. The opposite side has been treated quite differently. To capture and introduce natural luminance into the centre of the building, it has been made into a continuous louvred screen. Made of oak slats, it protects the offices' privacy, while throwing a changing pattern of lucent gold coloured stripes across the interior. Campo Baeza describes the process as 'combing the light'.