Other than a few churches, the only thing we got to look at properly on the Open House London weekend was the Guildhall. I've seen the outside of the building many times, and thought about including a detour to it from my London Wall Walk photo set http://www.flickr.com/photos/jimgunnee/sets/72157600537571233/ - as the arc marked out in the forecourt shows the extent of the Roman amphitheatre.
What I hadn't realised was the number of halls and the amazing quality of the interiors.
This is a view of the interior of the main hall - that is, the one you see from the courtyard in the view above.
There are some interesting monuments around the hall, including these to Nelson and Wellington:
This is its undercroft