I've only gone off of the articles. Generally that'd have to be some hellish fog though...Its been all over the news suggesting it may not have had a light on the crane, though I saw a recent pic of it on another site with a light on the crane
What's the law say? How high was the crane?
I can't speak on UK laws regarding this sort of thing in particular but I'm almost positive that every construction endeavor involving a crane or support is supposed to have its own lighting if it extends past the building that its related to.