The Houses of Parliament and Westminster Abbey, immediately upstream from the western foot of Westminster Bridge, are very fine and very grand items in this set and they are good examples of the two major reasons why a building may be considered to be of interest. It may be because of how it was built or because of what it is or has been used for. It doesn't seem entirely inappropriate that another item in the set is a working gas holder that is certainly the oldest in the UK and possibly in the world.