A mash-up by Christopher Gutteridge (@cgutteridge) at the University of Southampton. This uses Ordnance Survey postcode data or data from DBPedia to try to work out the correct orientation on a panoramic picture of London taken from the BT Tower. (open data for the win!). Oh, and it throws in a Google map + street view n/s/e/w views and an image from wikipedia if it can find one.
PRO TIP: obviously tall things are more likely to be visible. Street level is obscured. The camera should center more or less on the ground location of the thing, but you may need to pan slightly in some cases, such is life.
Thanks to Graeme Earl for the suggestion of this hacky little app.
For extra points, if wikipedia mentions the number of floors then the camera angle is adjusted to around half way up based on an estimated 4m per floor.
The code for this is a lashup, but if you are interested in it despite it's shonkyness; it's here: https://github.com/cgutteridge/TowerHack. What the hell, lets place it in the public domain.