Evacuation was the process of removing civillians from an area that was deemed to be under threat.
During World War II, many British children were evacuated from major cities. In 1941, the Blitz forced many children in London to be evacuated. Tom Flanagan was taken to Cardiff and then out to the countryside. (TV: Ghost Machine)
London was again evacuated in the 1970s after dinosaurs appeared on the streets. (TV: Invasion of the Dinosaurs)
UNIT evacuated the residents of Carbury after the town was attacked by Morgaine and her forces. (TV: Battlefield)
In an alternate world, people from London and the surrounding area were evacuated after a replica of the Titanic crashed into Buckingham Palace, causing a nuclear explosion. The Noble family were evacuated to Leeds. (TV: Turn Left)