Sometimes the mirrored glass panels fall off - it is just rough brickwork behind them as far as I can see !
Yup
Originally there was a problem with them breaking
it turned out (so I heard) that it was the landlord or the pub opposite who was smashing them with a high powered catapult and ball bearings
he was "annoyed" because the computer operators had been banned from nipping over there in quiet times
of which there were quite a few because they staffed the computer rooms based on what they might need - but when everything was going OK then some of them were just sitting around doing whatever (some stories about wheegee boards that I'll save for another time)
so they started nipping over to this scruffy pub instead and having a pint (or two)
banning them seriously screwed up his profits!!
anyway - he got caught when they put CCTV up - the appearance of several large cameras clearly didn;t make him stop and think!!!
but yes - behind the mirrors is just breeze block
originally it was supposed to be a rectangular building just built of brick but the council rejected it as not pretty enough for a new building on a well used approach to the business district
so they cam up with the curvy thing and mirrors to make the city look techy