Take the subway to Kensington High Street. On the street above, walk to the right for about 100 meters before turning down the first street on your right. Derry Street. It's the first door you'll see. Say hello to the uniformed man behind the marble desk and ask politely if there really is a garden on the roof. The man will nod at you, and all you'll have to do is sign your name in the visitors book and let the lift carry you to the top. The man behind the garden is Trevor A. Bouven DL, JP. (1878-1964)