New meets old -- the new contextualism.

The gradual evolution from designing semi-industrial buildings on edge-of-town sites to buildings of greater complexity and cultural significance in the centres of cities has moved the practice's architecture into a new and rewarding dimension.

You could characterize the development of Nicholas Grimshaw & Partners as a journey from the city fringes to the city centre. This convenient organizing device is of course disrupted by real events: for instance some of Grimshaw's earliest work, in the late 1960s and early 1970s, was in the centre of town. But since the present practice was set up in 1980, the trend has been a steady move from semi-industrial buildings on the outskirts, to buildings of cultural and symbolic significance and increasing complexity in the centre. Building in the outskirts, you often have to make your own context. Building in the centre, you have a context to respond to. Frequently modification of existing, historic buildings is called for. The architecture of the partnership has accordingly taken on a new dimension.

This is contextualism in the sense of an almost abstract response to the perceived character and proportions of surrounding buildings, coupled with the knowledge that the best contemporary architecture sits the more happily within its context if it is true to its own time. Few may notice, for instance, that the main elevation of the 1988 Sainsbury's superstore in Camden Town is divided vertically to reflect the party walls of the early Victorian houses opposite: but that subtlety is present.

For the competition-winning Caixa Galicia art gallery in La Coruna, Northern Spain, the presence of the city's tall narrow houses with their second skins of glazed 'gallerias' and shutters helped to generate the building's proportions and facade treatment. That was then melded with the functional requirement to bring daylight into a below-ground gallery and an auditorium foyer. The result is a vertical screen maintaining the street line, behind which is a facade that leans forwards dramatically from a point well back from the site boundary. This angled facade allows a generous glazed area to bring daylight into two basement levels, and serves as an additional sunshading device. Meanwhile the parabolic arched roof form neatly accommodates the transition between the grand, tall facades of the front and the lower, intimate feel of the Calle de la Estrella at the back Finally, a new alleyway is made from front to back, creating a public route through the heart of the new public art gallery.

A similar task faces the practice in Bath: to make a new spa building alongside restored and reopened Georgian examples. A number of practical challenges -- how to make a multi-level pool building and cope with the corrosive nature of the hot natural mineral springs -- are combined with the need to build in one of the most sensitive historic townscapes in the world. In the past Bath and Modernism have not mixed happily. But in this Lottery-assisted project, there is a civic will to make a genuinely distinctive new building. The site is a derelict municipal 1920s swimming pool alongside the disused Georgian Hot Bath and Cross Bath buildings. The commission is to restore these (in collaboration with Donald Insall Associates) as part of an overall programme that also includes the new building.

The new spa building picks up on the scale, height, materials and plan forms of its historic neighbours and distils these into something altogether new. A three-storey stone cube -- the main bathing complex, aligned with John Wood's 1775 Hot Bath next door -- rises through a glass enclosure that follows the street line. The cube is set against the secondary form of a corner staircase rotunda. Unlike the existing baths, the new one is a multi-level building, with both a ground-level pool and a rooftop one overlooking the city NGP is working with the acclaimed artist Vong Phaophanit on ways of expressing the beauty of light, water and steam in the new building and its surroundings, possibly forming a visual link with the Roman baths a short distance away.

There is a clear design link between the Bath project and the practice's second-placed competition entry for the Victoria and Albert Museum's 'Boilerhouse' extension, which played a related game of solid and void with its historic neighbours. Elsewhere, NGP has worked with other intriguing contexts; for instance the 'Beauty and the Beast' scheme in Hamburg officially called the Berliner Tor. There the plan was to marry the existing Brutalist 20-storey police headquarters tower to a new, very delicate latticework tower wrapped in a chameleon double-glass skin. The client however did not take kindly to the existing building being described as a beast. But still the practice persists in regarding context as a prime generator of new form, even when that requires structural gymnastics -- such as the aqueous roof of the lakeside pavilion project at Neuchatel in Switzerland, where the concept was nothing less than an uptilted section of the lake itself.

In other cases, the task is twofold in that the context is the actual building being worked upon rather than a close neighbour. This is true of the very different projects at Paddington Station and at Battersea Power Station. Paddington -- by Brunel, Digby Wyatt and Owen Jones -- is a Grade I predominantly nineteenth-century listed building that had to be significantly updated for twenty-first-century travel. This involved not only rail departures but also airline departures, since the station is now umbilically linked to Heathrow Airport. In the [pound]60m first phase of development the worst accretions of the postwar period were removed, the clarity of the Brunel vaults revealed once more, and the concourse was extended into a complete new building set back from the original concourse in the area known as 'the Lawn'. Here a ridge-and-furrow glazed roof system was developed. Such a system would have been familiar to Brunel from Paxton's Crystal Palace, but in contextual terms it works here, as the original nineteenth-century canopy did, by being so clearly different from the existing vaults. This [pound]60m job is just the start, however. Phase two of the work involves constructing a complete new concourse down one side of the Brunel building on the site of a 1916 train shed, opening it up to the presently hidden canal basin alongside, and -- by means of a remarkably ambitious and beautiful transfer structure -- adding buildings, including a 42-storey tower perched high on top.

Battersea -- the huge power station left semi-derelict and open to the sky at its heart -- requires urgent remedial attention. Here NGP proposes inserting what is effectively a completely new glazed building into the hole, rising on tall columns to provide an inhabited roof level with a cyclopean belvedere of a west wall. The contrast of old brickwork with the crystalline nature of the new structure is a classic Modernist move. Closer inspection reveals, as you would hope, that this is no ordinary glazed structure. Rather, it is one that includes an innovative 2500 seat theatre, the backwall of which curves and rises to join the undulating draped roof form high above.

You find a great tectonic confidence in NGP's handling of such work Buildings change, uses change, technologies change, yet the past holds important lessons. NGP could never be accused of being overawed by history: but the respect is there. The context is a prime generator of the architecture.