We then took the underground back in to town and met my Dad at St. Paul's Cathedral, it's so huge and the photos don't convey it's size at all.

We walked up the stairs to the whispering gallery which is a huge round balcony that looks down in to the cathedral. Apparently if you stand on one side and whisper, the person on the other side can hear you.

We then walked up to the very top, which gives you a great view over London.