Portrait of the artist.

At London's National Portrait Gallery, the lyrical remodelling of the nineteenth- and early twentieth-century galleries shows the paintings in a new more graceful light.

The National Portrait Gallery in London was set up in 1856 to celebrate the men and women who shaped public life, and also to contribute to understanding of the art of portraiture. As an institution it has a pushme-pullyou character, quite unlike that of the Tate or the National Gallery - but entirely in keeping with the split identity of portraiture. Different directors have chosen to emphasise one or other aspect of the genre. Under the ebullient Roy Strong the trend was to be documentary and modishly up to date. Under his successor John Hayes, the emphasis shifted towards portraiture as an art form. The present director Charles Saumarez Smith is an interior design specialist from the V&A, and it is already clear that under his stewardship the fabric of the NPG is going to change far more radically than its contents. A bold scheme devised by Edward Jones and Jeremy Dixon, and funded with lottery cash, will insert a new lecture theatre, a cafe and a spacious entrance hall into a slot between the National Gallery and the NPG - for all of which we must wait until 1998, or later. Meanwhile, the director has already issued his manifesto, in the shape of new nineteenth- and early twentieth-century galleries, remodelled by Piers Gough.

The fact that in the week of their opening these galleries stirred up a pseudo-controversy (what no Ruskin? bellowed The Sunday Telegraph) merely confirms that architect and client have done a good job. Obviously, there are gaps in the NPG - as in other collections - and with a miserly purchasing grant of [pounds]300 000 it is difficult to see how these could be adequately filled. What the NPG can do, though, is convey a flavour of a period, and this has been splendidly brought off in Gough's tactful but imaginative conversion.

Gough is one of few architects at work in Britain whose touch is instantly recognisable. Even so, so reticent has he been, and so excellent the quality of most of his workmanship, that it is often difficult to distinguish between his insertions and the uninspired 1896 original (by the ecclesiastical architect Ewan Christian). Yet the Victorian galleries have been transformed. Daylight has been admitted through angled rows of teak shutters to existing but previously blocked-up windows and the lighting layouts have been completely overhauled. The existing inadequate lecture hall now becomes part of the hanging space, allowing the curators to be more generous in their spacing of exhibits.

Excellent use has been made of sculpture. In the introductory gallery which acts as an appetiser to the Victorian galleries, a life-size Victoria and Albert sculpted in medieval costume is the first item to catch the eye with, beyond, a cascade of black plaster busts of Victorian worthies arranged in tiers as if they had been pulled out of the drawers of some giant plan chest. The central gallery becomes an alley of statesmen, with portrait busts jutting out from the wall on projecting plinths on either side and culminating in James Guthrie's blockbuster - 11 years in the painting - of the 'Statesmen of World War I'.

The galleries are arranged thematically, with rooms devoted to politics, the arts and sciences, and Empire. Walls have been clad sympathetically in maroon and olive green and grey shot-silk and - a master stroke by the architect - some of the portraits angled out from the wall plane. This is an entirely justifiable way to mount what are, often, quite second-rate paintings. Portraits en masse, unrelieved by landscape or still life, can become tedious viewing. This simple device gives energy and rhythm to what sometimes threatens to become a relentless parade of bewhiskered old gentlemen. It is with some relief that one reaches the turn-of-the-century gallery. Not only is the mood lighter but the portraits are better: no fewer than five Sargents, a superb William Nicholson (of Max Beerbohm) and a famous self-portrait by Gwen John. This raises the spirits as one passes through the transitional First World War section (T. E. Lawrence and a galaxy of admirals and generals), to the twentieth century beyond.

Here Gough sheds his self-effacing mock-reverential manner and starts to enjoy himself. The Duveen Gallery (formerly devoted to special exhibitions) used to be dark and sepulchral. Now it is flooded with daylight. A ceiling with slots cut into its double curvature hovers over what appear to be free-standing glass cases. Portraits are hung on the outside surfaces of these, as well as on the walls, and the glass is punctuated with 'bull's-eye' recesses, to receive hanging brackets.

The effect, combined with a floor of broad oak planks, evokes something of the spirit of the Festival of Britain. Gough is not perhaps at his best when working out a design in meticulous detail. One might quarrel with the ambiguous way in which the glass screens appear to rest on the floor plane, when in fact they are supported from below on steel plates. Other details though, such as the curved metal portrait plinths, have all the bite and freshness of an original sketch.

One can continue to find fault with the hanging policy of the NPG as well as lament the gaps in its collection. In many cases there is an inverse ratio between the significance of the individual and the size of the portrait. As a general rule Nobel prizewinners rate a snapshot, whereas pop stars and hairdressers merit a hoarding. No matter. These lovable inconsistencies are part of the nature of portraiture and part of the charm of the NPG, Ruskin, or no Ruskin.