Brutalist Architecture was most popular in the 1950s - mid 1970s worldwide. Its distinct concrete block form is easy to identify in many cities. Interestingly in London, a Brutalist style building likely replaced a WWII bombed site because it was relatively inexpensive and quick to build. The banks of the River Thames was particularly hit hard during WWII.
National Theater in London
Fortunately, the beautiful Tower Bridge was spared because it was an important aerial landmark to the Germans.