Mirror mirror

The mirror glass office block on Euston Road is a rarity, a huge building completely covered with an impenetrable skin of mirrors, right down to pavement level, so perfectly reflective as to give no hint of what might be happening inside. It stands out from its surroundings, reflecting the other buildings and on occasion drenching them with reflected light. Yesterday the low morning sun was bouncing off the mirror surface and covering the green and white hospital opposite with strangely intense dappled brilliance. Later in the day it often has a similar effect at the bottom of Euston Tower, with everything in deep shade except where the reflection hits, picking out the buses in a luminous bright red. Crossing Euston Road at lunchtime, you can walk into a pocket of brightness and be suddenly dazzled. But at least the facade is flat - so there's no question of the buses bursting into flame.

The building itself is tall and bland, reflecting the dull grey of overcast days, or deep blue and fluffy white summer skies. Move a bit closer and you get reflected plane trees, overlaid with the actual trees that line the pavement, the whole thing neatly divided up into rectangular panels by shiny chrome glazing bars. The glass isn't perfectly flat so all the reflections are distorted, quite a pretty effect. Closer still, you walk past trying to resist the temptation to watch yourself in the mirrors, not knowing if someone inside will be thinking, what a dick... you can't tell. Reflective glass is usually two-way to some extent, but this is apparently one hundred percent one-way mirror. You walk past wondering what goes on inside, what possible reason there might be for such intense privacy. But it's just the architect's conceit, a fad for using the latest glass technology of the time to glitzy if tasteless effect.

Oddly, the strong impression of opacity diverts you from realising that the building is not really opaque. I must have passed the place hundreds of times, and imagined perhaps twenty companies inside, dingy corridors and grubby carpets, but completely failed to realise that you can see inside if the lights are on, vaguely. Especially after dark, the strips of window are lit up almost like any other office building. That does allow a dim view of typical cluttered offices - the dimness makes it seem claustrophobic.

Finally, on impulse, I walked in through the entrance doors, encouraged by the constant flow of people in and out. Like any office building, it has an open front entrance, a lobby and reception desk, so I walked in along with the lunchtime crowd and stood there trying not to look conspicuous. I needn't have worried. The building is entirely occupied by University College Hospital and heaving with activity. It’s evidently an enclosed world known only to those who work there. Comings and goings are controlled, loosely, from the front desk. But you can walk straight through to a rather good canteen, incongruously set in a glazed vault, a pastiche version of a Victorian arcade, all green metal, bricks and potted palms.

It's antisocial and dated, a typical expression of the crass commercial architecture of the late 1970s, but in its way also rather special.