A light installation has appeared just round the corner from the flat. We're pretty close to the London Olympic village so it could be related to that, although if it is, I think it's a tribute from the offices in the background rather than official London 2012 stuff.
My evidence for this is that it's really cool and doesn't feature disturbing one eyed trouser monsters, as all the official stuff does (and isn't).
Anyhow, I actually planned to take a photo of this reflecting in the canal but the sky was so striking I changed my plans on the scene. I'll try and find out who/what/why put it up before I do any more pictures of it.