The Most Beautiful Structure in London

In my humble opinion, as viewers of my Instagram feed will know, the most beautiful architectural triumph in London is St Paul's Cathedral.  If you haven't actually ventured inside it and walked all the way around it on the exterior, you haven't seen St. Paul's. It's Goodness, Truth and Beauty combined for all time.  An added bonus is that the cathedral's Institute often hosts some thought and action-provoking lectures and debates, such as the recent one about capitalism and post-capitalism with Paul Mason, Ann Pettifor and Phillip Blond.