Although attacked by one critic when it opened in 1896 as 'a violation of good taste and architectural proprieties', the National Portrait Gallery (npg) was actually a sensitive and, by Victorian standards, remarkably contextual addition to the fabric of central London. Its architect, Ewan Christian (best known for rather pedestrian Gothic Revival churches), chose an eclectic Renaissance style for the building, which was tacked on to the back of Wilkins' Greek Revival National Gallery. On the St Martin's Place frontage he even deigned to replicate Wilkins' Classical detailing (then deeply unfashionable) to ensure a seamless join.
As a consequence of Christian's well-mannered approach, the npg appeared to be a mere addition to the National Gallery. Nor has the £16 million npg 2000 project, designed by Sir Jeremy Dixon and Edward Jones and open to the public on 4 May, done much to correct that impression - it could not, since external changes to the listedfabric were effectively ruled out. Dixon.Jones' new wing has no external face. Yet, behind the Victorian facades, the npg has been transformed, visually and operationally. The project is arguably the most radical in its impact of any of the London museum projects coming to fruition this year.
The confined site gave Christian's building an unavoidably vertical character. Visitors came into a cramped entrance hall and were immediately confronted by the staircase - the ground floor was originally used as offices and storage space. The addition of the 1930s Duveen Wing (tucked away in Orange Street) did little to improve visitor amenities. Even Roy Strong, appointed director in 1967, was unable to tackle the basic defects of its premises, though he did wonders for its hitherto fusty image and visitor numbers - not least by displaying portraits of the living, as well as the illustrious dead. A 1988 initiative to erect new galleries on the far side of Orange Street (which produced a striking scheme by Stanton Williams) came to nothing. Attention switched back to the Christian building, where John Miller's new ground-floor galleries opened in 1993. (The npg offices went into a design-and-build block on the Orange Street site.) Used to house the contemporary collection, they did much to boost attendances.
Charles Saumarez Smith, Dixon.Jones' client, architectural historian, and npg director since 1994, saw the need 'to stand back from the gallery and its recent development and consider what were its longer-term needs and to try to plan how these needs might be accommodated, not in a piecemeal fashion, but more purposefully'. Dixon.Jones' appointment, at the end of 1994 has resulted in a complete overhaul of the gallery, with public and display space increased by 50 per cent.
In recent years, npg visitors have poured into ground-floor galleries and then drifted, in diminishing numbers, upstairs. Though the opening of Piers Gough's nineteenth- and twentieth-century galleries in 1996 (another Saumarez Smith commission, aj 31.10.96) provided a draw on the first floor, many never made it to the top floor. Now most visitors will jump straight on to the 23m long escalator (claimed as the longest in London, outside the Underground) and ascend through a full-height daylit space, where intermediate floors appear to float, which has become the heart of the transformed npg. From the second floor, they will make their way downwards through 500 years of British history, from Richard III and Sir Thomas More to Tony Blair and Oasis.
This remarkable expansion programme has been made possible by what Dixon.Jones refers to as 'the Deal'. At the rear of the Christian building, accessed off Orange Street, was a delivery yard owned by the npg. The fact that the National Gallery had offices overlooking the yard and, consequently, rights of light, seemed to rule out anything but a thin wedge of building which would be of little practical use. 'The Deal' involved an agreement with the National Gallery - the latter gained control of the npg's St Martin's Place wing in exchange for surrendering its rights of light. The npg has finally been able to develop its backyard.
Saumarez Smith describes the new central hall as 'a kind of three-dimensional architectural map of how the building works'. Though superficially in the spirit of Norman Foster's Sackler Galleries at the Royal Academy, the Dixon.Jones project has a far greater impact. It cannot be ignored, whereas it is possible to visit the academy and be unaware of Foster's intervention. At every level in the npg, the new wing abuts and opens up the nineteenth century building. On the second floor, the enclosed Tudor galleries, their walls covered in slate grey fabric ('like soldiers' overcoats', says Dixon) lead through to the elegantly refurbished rooms containing the seventeenth and eighteenth century portraits. Piers Gough's nineteenth and twentieth century galleries are now supplemented by a late twentieth century gallery, literally suspended above the central atrium. A series of staggered partitions partly enclose this space, allowing views in and out. Linking the atrium (named after major donor Christopher Ondaatje) to the existing staircase and floor levels entailed some nifty adjustments in levels and some skilful reworking of historic steps and mosaic floors, but the smoothness of the connections impresses. Though effectively a free-standing building, the new wing is opened up at every level by the use of huge timber doors, fixed back during opening hours. From the second- floor galleries, for example, you can see straight across the atrium and glimpse Nelson on his column through the clerestory windows.
A pre-emptive strike by Dixon.Jones in 1999 gave the npg an attractive basement-level cafe and bookshop. The main gift shop remains where it was, at ground level, courtesy of a lease-back from the National Gallery - Saumarez Smith has had the courage to declare the new atrium a retailing- free space and a raised area once envisaged as a shop has been filled with it equipment and comfortable seating. A well-equipped auditorium has been placed at basement level. Decorated in the grey/white/natural wood palette found throughout the new wing, and panelled in slatted timber, this is a sober, even grave, room. The row of columns along one side supports the escalator, but has a symbolic role too, reinforcing the asymmetrical theme which runs through the building.
In a Dixon.Jones project one expects to find a painstaking approach to detail and a concern for materials and textures - the quality of the oak gallery floors and fitted furnishings in the npg is well up to scratch. These are architects who can be high-minded, but who equally like to enjoy life. The restaurant perched on top of the new wing, with views across the National Gallery's roofscape of domes, towers and rooflights is an ingenious move, achieved against the odds. (Westminster planners were determined to make the space invisible from below - 'why it should be invisible is, in principle, questionable', says Edward Jones.)
Charles Saumarez Smith was clearly a demanding, though sympathetic, client, with a strong personal vision and definite taste. (He made no secret of his loathing for the neo-Victorian revamp of the entrance hall and staircase designed by Roderick Gradidge, completed in 1990 and now totally expunged.) Saumarez Smith envisaged a new building with 'a strong sense of systematic, incremental and purposeful, organic development' ... 'classical, modern, cool ... intelligent and lucid'. These adjectives could, without undue hyperbole, be applied to the completed scheme. Dixon.Jones' skill as gallery designers was already evident in its Henry Moore Centre in Leeds - the cube gallery there is memorable for its use of diffused daylight. The npg has turned out to be a landmark scheme for a practice in whose work formal preoccupations have sometimes blurred an essentially practical agenda. At the npg, Dixon.Jones has cast off the historicism still evident in the Royal Opera House - parts of which were designed in the mid 80s - while adhering firmly to the civic concerns which link them to great urban architects like James Stirling and Aldo Rossi. 'It's a matter of bringing the street into the building,' Jones says, looking through the new lightweight entrance screen on to Charing Cross Road. Dixon.Jones's npg is about bringing not just the street, but the city, into the museum: making it a place to relax, reflect, have a drink or a meal, think about history or art (the npg is about both) or simply enjoy the spaces. The Royal Opera House is bigger and grander, but, in its way, the npg is just as significant for London and for its architects. No wonder that Sir Jeremy and Mr Jones have now been added to its valhalla of British worthies.