Waterloo churches / Commissioners' churches
Following the defeat of Napoleon at the Battle of Waterloo a Commission was set up to build churches as a means of giving thanks and commemorating the victory.
The churches are also known as Million (Act) Churches because that was the sum, £1m, initially granted for their construction, in Acts of 1818 and 1824. Wikipedia provides a list of the churches that were built in London.
Not to be confused with the 1710 Commission for Building Fifty New Churches in and around London, which became known as Queen Anne Churches.