Architects get their inspiration from a myriad sources, but Downie is happy to acknowledge a currently unfashionable one: a sunken, curving extension to Keble College Oxford, done in the mid 1970s by architects Ahrends, Burton and Koralek, who were later to achieve unjustified notoriety for their aborted plans to extend the National Gallery. The Keble project, like the RGS, was a device to get public space - in that case a students' bar - into a landlocked garden setting, a then-new residential quad. Downie reasoned that it had worked once, was a brilliant formal solution, and could therefore work again if the same thinking was applied to a London building of similar period. He was right. It does.

So now, if you walk up Exhibition Road, the spine route of Albertopolis, you start with the mighty V&A, pass the Natural History and Science Museums, press on up past Imperial College towards the park and there, on your left, you find that the RGS has arrived at a point where there used to be just a wall. The pavilion in brick, concrete, glass and silvered copper sits back behind a balustrade of glass etched with images from the Society's collection by artist Eleanor Long. It is an entrance point and exhibition gallery, where you'll find the inaugural show "Unlocking the archives" with some rare photos, maps, and information on some explorers other than the obvious ones. At the entrance, Downie has picked up and physically framed a view along the backs of the Kensington Gore buildings to the Albert Hall: it's the first thing you see, Albert's flying saucer floating eerily behind layers of glass.