Williams’ conversion of Baltic is an entirely new building inside the old shell. It is very assured. True, he inherited a gift of a layout. The old 1940s flour mill may be anything but elegant externally - in fact its proportions are distinctly odd - but it is very nearly square. Hence the wide open spaces inside it, which are floored simply with lightly limewashed Scandinavian pine boards. Other materials are kept equally simple- riven slate, pre-oxidized steel, frameless glass, stretched-fabric ceilings. Williams explains that with no art collection to design for, and no knowledge of what artists might make of the building, there was no point trying to get too precious about it all. So you get five levels of galleries, a digital editing suite, an auditorium, a performance art space, and rooms for artists-in-residence. On top of the old building are a viewing gallery and a restaurant, while a new low two-storey building with a curving silver roof - an architectural flatfish - is placed at the western end as an entrance, with café and shop inside.

Baltic’s director, Sune Nordgren, describes the place as an "art factory". Williams and his structural engineers, Atelier One, have taken him at his word, designing the building pretty much as if it still had an industrial use. The new floors are very strong indeed, and there is a capacious heavy-duty goods lift. You can drive trucks in downstairs, and put a Sherman tank on the fifth floor if you are so minded. Above that, the restaurant is a new structure sitting on tubular steel trusses, echoing the grandstands of the St. James’ Park soccer stadium that dominates the Newcastle skyline. But the best views are westwards, through the glazed end of the building, up the Tyne gorge. On every level - and from the glass lifts that rise up this end of the building, and from an open terrace on the northern side, and especially from the "viewing box" at the top which projects out from the facade - this new view of the succession of famous Tyne bridges old and new is framed, exploited, made to work for its living.