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High and mighty

STIRLING PRIZE 04

Foster's building for Swiss Re, this year's winner of the Stirling Prize, sponsored by The Architects' Journal, is both a simple statement and a building of great complexity. We examine some previously unconsidered aspects of the building, consider the runners-up and look at the winners of the specialist awards that were announced at the same time

The real driving force behind tall office buildings, AJ critic Martin Pawley argued, 'has been the production of an enclosed interior landscape, a process whose external drama has been drained by repetition for nearly a century'. In its reinstatement of 'external drama' as a key element in the design of the tall building, Foster and Partners' 40-storey 30 St Mary Axe tower (formerly Swiss Re) has captured the public imagination and was the popular, as much as the critical, choice for this year's Stirling Prize. The award was also a welcome reassertion that the design of workplaces matters as much as that of the public, cultural and infrastructural projects that have virtually monopolised Stirling since it was established.

It was Louis Sullivan, a pioneer of building high, who insisted that tall buildings should express the drama of their structure - 'where imagination is absent and its place usurped by timid pedantry, the case is hopeless, ' he wrote.

Foster's tower, its striking form boldly developing (with the aid of advanced computer modelling) the possibilities of the diagonally braced structural skin, has become a London landmark, a symbol of the capital and a component in an increasingly variegated skyline.

Tall buildings have long been a contentious issue in London. It is nearly 70 years, long before the advent of modern high-rise buildings here, since the City promulgated the St Paul's Heights Policy to protect distant views of Wren's cathedral. At 180m, St Mary Axe easily oversails its 1960s (though recently reclad) neighbour, GMW's Commercial Union Tower, on the site of the former P&O Building - though, probably deliberately, it allows the NatWest Tower (completed in 1981 and now renamed Tower 42) to retain its pre-eminence as the City's tallest building. The location of Foster's tower in a cluster of tall buildings in the eastern quarter of the City was a strong argument in its favour and helped to secure the blessing of English Heritage (which later, inexplicably, launched an unsuccessful campaign against KPF's proposed Heron Tower on Bishopsgate). Richard Rogers'Leadenhall Tower, 42m taller than St Mary Axe, is set to join the cluster, standing across the piazza from GMW's tower.

The Commercial Union complex, complete with its Manhattan-style 'plaza', was widely admired when new, though the sunken square is a joyless, dank space, barely populated even on a fine day, a place of passage, not of lingering. It exemplifies the problems involved in transporting an urban form associated with the North American grid city to the City of London, with its random, basically medieval, street pattern. (The City's failure to radically reconfigure its urban plan was widely criticised by progressive architects and planners as post-war reconstruction got under way in the 1950s. ) A decade on, Rogers' Lloyd's, itself essentially an insurance market, positively embraced the intimacy of the neighbouring Leadenhall Market.

The site for 30 St Mary Axe was created, of course, by the 1992 IRA bomb that wrecked the Baltic Exchange, a lavish but, in truth, not especially distinguished 1900s structure.

Initially, developer Trafalgar House commissioned GMW (which had remained a major player on the City scene) to examine potential development strategies for the site; the chosen solution was a medium-rise groundscraper filling the available land. In August 1996, however, Foster unveiled alternative plans for a London Millennium Tower there, 385m high with up to 150,000m 2 of mixed-use space.

These plans were highly controversial and eventually withdrawn by Trafalgar House early in 1998. Swiss Reinsurance (Swiss Re), which occupied a number of buildings in this quarter of the City, took an interest in the site late in 1997. The Foster scheme was developed by Swiss Re in association with Skanska, as successor to Trafalgar House.

'A building is only as good as its client, ' Norman Foster has declared, and Swiss Re, with Carla Picardi and, latterly, Sara Fox coordinating its involvement, proved an admirably supportive client. Swiss Re is in the insurance business, at the receiving end of the disastrous effects of global warming, so that, as Foster project director Robert Harrison reports, 'its attitude seemed remarkably environmentally progressive - they liked the idea of a building with a strongly sustainable image'.

Foster sees St Mary Axe as 'a considered attempt to break down barriers and improve the quality of life in the workplace'. If the sculptural, curvilinear form of the building (which attracted Stirling judge Antony Gormley) has precedents in earlier Foster projects such as the Bilbao Metro and Canary Wharf Station, the issue of rethinking office design is one that has preoccupied Foster since Team 4 days. Willis Faber, the Hongkong Bank and the Frankfurt Commerzbank (credibly claimed as the first 'green skyscraper') are landmarks in the quest, which continued in the Foster scheme for the World Trade Center site.

The site of 0.57ha was an irregular rectangle, bounded by two narrow passages to the north and south and with the modest thoroughfares of St Mary Axe and Bury Street (with Berlage's famous Holland House) to the west and east. The Baltic Exchange had filled it completely. The churches of St Helen, Bishopsgate, and St Andrew Undershaft, both precious survivors of the Great Fire, are near neighbours. The latter was formerly the site of the City's maypole (higher than the church tower before its destruction in 1547) and one of Foster's drawings playfully refers to the new building's possible 'maypole effect'. (The spiraling light wells clad in grey glazing, and the use of paint to emphasise the vertical fourstorey diamonds in the diagrid cladding, with horizontal elements played down to reflect the structural agenda, emphasise the verticality of the tower. ) While much attention had focused on its long-distance impact, Foster was equally concerned with the way the tower would be experienced at close hand. 'The City within a city has always been full of surprises, ' he noted. The most impressive views of St Paul's, for example, are the incidental glimpses seen through gaps in the building line.

The most obvious public gain in the project was the opportunity to turn most of the site into public space - the tapering shape of the building means that the footprint is quite small (just under 50m across) and that it is perceived from the ground as less high than it actually is, while minimising down-draughts at street level. Foster's aim in workplace design over 40 years has been to 'open up the office, ' but at St Mary Axe he has also succeeded in opening up the City. Thousands of City workers routinely cross the site daily, following the natural axis that extends between Liverpool Street and Fenchurch Street stations. The success of the completed building consists, to no small degree, in its rejection of the constraints imposed by existing street lines - ideas of a podium or perimeter buildings along the northern and eastern edges of the site were discarded during the planning negotiations.

While other recent City office projects take their place in established contexts (one thinks of Foster's Wood Street, Gresham Street and Finsbury Square projects), 30 St Mary Axe creates its own context. The intention is that the piazza should develop a life of its own, with shops, cafes and a restaurant contained within the ground level of the tower, and the subsidiary block to the north that frames the ramp to basement level for service vehicles.

The 3,500 people who could eventually work in the tower - Swiss Re, in the event, has sublet about half the space - will make an impact on this sector, making use of public space that was once inside a City block.

The great strength of this project is the degree to which every aspect of the programme - social, structural, environmental, spatial - is fundamental to the whole. In its entirety, it represents the realisation of aspirations that have been present in Foster's work for many years. It is claimed, for example, that, largely thanks to the double-skin ventilated facade, energy consumption is potentially half that of a prestige air-conditioned office building of similar size (though fine-tuning by the building's users will be critical in this respect). Foster and Partners claims that this is 'a radical building? a paradigm of the responsible environmental practice that is a quest for both architect and client'. For Norman Foster, it is the practical embodiment of Buckminster Fuller's vision of 'a micro-climate within an energy-conscious envelope'. It is also a highly disciplined, rational building that recalls Foster's longstanding interest in Mies - you could call it Mies with a twist.

For the public, 30 St Mary Axe remains the 'gherkin', a nickname that doubtless makes the Foster team squirm. But how many office buildings in London have any public image at all? Londoners have taken to the Foster tower because it is shapely and recognisable from a distance - whether seen from the heights of Camberwell or the flat expanse of the East End - and sensational at close range, a defining landmark. But the glamour of the project should not obscure its genuine radicalism.

The inherently conservative City of London has not seen innovation on this level since the completion of Lloyd's nearly two decades ago.

It is only to be hoped that 30 St Mary Axe has established a measure of quality for new City buildings that will inspire others.

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