I saw it, agreed it was quite low that morning. Sometimes its good just to hit them with a tweet (if you use it) and ask. Lower than usual would usual mean low cloud base, or possibly avoiding the London City Airport flight path.

Having spent time over at Lippitts with them, they do indeed have amazing optics.

Their twitter feed is a goldmine of info and facts, and well worth a follow for info just like this.
@mpsinthesky