Martial law

Martial law was a state of government in which military leaders took power if civilian ones failed to do so. The Marshal of Solos took power under martial law after the death of the Administrator. (DW: The Mutants)

Brazen places the human colony on Frontios under martial law after the disappearance of Plantagenet. (DW: Frontios)

In the aftermath of the spaceship crash in the Thames and the dissapearance of the Prime Minister in March 2006, General Asquith threatened to impose martial law when Acting Prime Minister Joseph Green, along with Oliver Charles and Margaret Blaine, didn't take the events seriously. Their strange behaviour was revealed when they revealed themselves to be members of the Slitheen family before killing Asquith. (DW: Aliens of London)

In an alternate timeline, a state of martial law occurred after the emergency government failed to maintain control. (DW: Turn Left)

In Pete's World, London was placed under martial law after the Cybermen moved into the city and the EarPods were activated. (DW: The Age of Steel)