What would otherwise be a rather claustrophobic shoebox shape is relieved by the fact that a freestanding side-wall slices across the space at a narrow angle. The glazed gap around the wall where it punches through allows more light to flood in. And that is it - that is the complete architecture of the church. It is to do with space, light, and texture. These are the fundamentals that British architects, still much obsessed by style, would do well to study.

Though tenaciously Japanese in outlook, Ando has broken out of the Orient with commissions in Germany, Italy, and now America, where he is building two art museums. What, though, of Britain? He came close to winning the competition to build the Tate's Gallery of Modern Art on Bankside - the model and drawings, showing the old power station lanced through with great projecting glass galleries, are in the RA show to remind us of what we've missed. But the day he was in London in January 1995 to present his scheme, he learnt of the earthquake which devastated the city of Kobe, close to his own base in Osaka. He flew straight back. What he saw there has, he says, made him think more deeply than ever about what he calls "the manner in which architecture acquires life".

Typically, one of his first acts was to propose planting thousands of magnolia trees all over the city, their frail whitish-pink flowers blooming every spring in remembrance of the dead. The city responded: money was raised and the trees have been planted. Now he is contributing architecture, in the form of a new museum and waterfront plaza. Japanese cities, he points out, have few public gathering-places.

Japanese pavilion, Expo '92, Seville

The new Ando is turning increasingly to glass to open up his buildings more to the outside world. He likens his use of transparent envelopes around his solid buildings to the traditional Japanese veranda or engawa: a space that mediates between indoors and outdoors. This may have the effect of making his austere architecture more palatable to conservative western nations such as ours: but Ando gives the impression of being in no hurry. If he ever builds in Britain, he says, he would like a city location resonant with tradition: that is why he liked Bankside, and part-icularly Shakespeare's Globe theatre alongside.

The man may sound over-serious, but this is not the impression that this stocky and cheerful ex-pugilist, much given to bursts of laughter, conveys. He signs a book in a thick silver felt tip, adding a tiny drawing of the Church of the Light in a few swift lines. He bows formally and shakes hands. Then he gives someone his camera and has our photo taken together, as Japanese tourists are wont to do.