Royal Festival Hall has had its exterior covered up. I am referring to the Centre Point tower which was one of London's first skyscrapers and completed in 1966. According to Wikipedia the site was once occupied by a gallows which is news to me and adds a gruesome touch to the area.
It became controversial because it was built by the property tycoon Harry Hyams who was happy to keep it empty for years until he could find a single tenant for the entire 34 floors. This led to all sorts of conspiracy theories, for example a designer I met who worked in Soho confidently told me it was built as a tax dodge and I've just read on the internet a few other explanations for this odd behaviour.
It used to have a rather elegant pool complete with fountains on its west side but all that has been demolished because of the ongoing Crossrail Project and this is the view you get at the moment until 2018 when Crossrail should be finished.