Canary Wharf aircon
I spent 3 months on the 10th floor of 1 Canada Square (*the* Canary Wharf tower, for those of us old enough to remember it in Long Good Friday era and immediately afterwards). The whole floor was being used as teaching/lecture space, so only had about 2 PCs on it. Unfortunately, the building and associated systems had been built on the basis that every desk would have a PC & CRT monitor pumping out heat - so there was an overabundance of cooling, and no heating at all. As a result, we were sat there in an August heatwave, clustered around 3 hastily purchased fan heaters, because every floor on the building was cooling for all it was worth and the "natural" temperature had settled at about 10 degrees celsius.
Around that time, there were constant grumbles from the management company, because all the excess heat was vented out the roof resulting in plumes of what one local resident thought was smoke. So every other morning, he rang the fire brigade & triggered a callout, which by this point were costing the owners about £20k a pop.