Gordon Benson and Alan Forsyth met at the aa more than 40 years ago and have worked together ever since. Both came to London from gritty cities - Benson from Glasgow and Forsyth from Newcastle-upon-Tyne. They formed Benson & Forsyth in 1978 and have now nearly completed their masterpiece to date - the Museum of Scotland - in Edinburgh, one of the most elegant historic cities in Europe. The museum, due to open in the autumn, is a building which defies the fashions and fads of recent years and, 'confident in its own modernity' (as the critic Duncan Macmillan has described it), 'conducts a creative dialogue with the traditional architecture of Scotland'. In other words, it succeeds - where most Post-Modernist buildings fail dismally - in coming to terms with history.
Gordon Benson is not a man to mince words, particularly when it comes to PoMo architecture. 'I would place its practitioners in the third circle of hell,' he says, 'where Dante placed the flatterers and falsifiers.' Nor is he attracted by the High-Tech tradition - 'like obsessive body- building . . . unnatural. . . turning architecture into a branch of industrial design'.
In the absence of his partner - busily at work in Edinburgh, where the practice has had an office since winning the Museum of Scotland in 1991 - Benson is left to expound the firm's own philosophy of design. He is never lost for words. (Not surprisingly, he has a glowing reputation as a teacher and holds a visiting chair at the University of Strathclyde.) He still feels very angry about the 'end of the welfare state' engineered by Mrs Thatcher. Housing had been Benson & Forsyth's passion. They did a decade, working as a team, in the housing department at Camden Council, including a stint on Alexandra Road with Neave Brown. The work of Powell & Moya was much to their taste and in the early 1970s they designed a group of 'nice, white houses' close to Powell & Moya's earlier housing scheme in Lamble Street, Kentish Town. 'In a way, we reinvented the house,' says Benson. Where Powell & Moya settled for a simple two-storey section, Benson & Forsyth went for a more sophisticated two-and-a-half-storey section which has more in common with the London terraces of the eighteenth and nineteenth centuries. There were other housing schemes, all of them explorations of the section. But then came Thatcher and 'that was it - simply no more housing', Benson recalls.
The early years of the practice were, not surprisingly, relatively lean ones, with teaching (at the aa) supplementing practice. Instead of housing, there were houses, including one for the singer Alison Moyet, and the wonderful, much-illustrated chapel for a nursing home in Cumbria. But Benson & Forsyth longed to build in the city and on a civic scale. At the aa, they had come to oppose Corbusier's urban ideals - 'they helped to destroy Glasgow', says Benson - but to love his late works, Ronchamp and La Tourette, in particular, in which he revealed his profound feeling for history. The practice's more recent work has reflected a desire to root modern architecture in time and place, respecting physical and cultural context. The Museum of Scotland was a dream of a job into which it has thrown itself heart and soul.
Benson is full of praise for the late Marquess of Bute, 'a great patron' who chaired the building committee in Edinburgh. He cannot really understand why good architecture has to be 'sold' to the public and loathes the 'grossly distorted, ugly' perspective by Carl Laubin which has formed the stock image of the building so far.
As the wraps come off, the reality of the museum is there for all to see. Its architecture derives partly from the needs of the collections but equally from the building's location, mediating between the Edinburgh of the Middle Ages - the Old Town - and the spirit of the Enlightenment expressed by Robert Adam's nearby University. The Museum of Scotland - and Benson & Forsyth's building is, of course, an extension to a Victorian pile - is, like the Soane Museum, a place where architectural setting and contents are closely integrated. After the breakthrough of the museum, Benson & Forsyth went on to win competitions for a new public library in Edinburgh and for an extension to the National Gallery in Dublin. The practice is also on the shortlist (of 12) for the Scottish commission of the new century - the parliament building to be built next to Holyrood House. If Benson & Forsyth, the only Scottish practice not allied with a big outside name, is in the next four, its scheme will be something to see.
The practice's interest in the regional dimension of modern architecture does not diminish its internationalism. It has completed two extraordinary buildings in Japan and produced a remarkable scheme for the v&a 'Boilerhouse' site. It's reassuring to know that Benson & Forsyth's commitment to London remains strong. 'We're out of place here, maybe,' says Benson. 'We're neither commercial nor High-Tech - but we've no intention of leaving.' When the magisterial quality of the Museum of Scotland is recognised, London too may find a site where the practice's talents can find full expression.