In 1963, the Judoon captain led a platoon of Judoon to the vault-planet of Janizzar, where the Cybock Imperium were attempting to steal the Time-Gun of Rassilon from one of the planet's vaults.
The Judoon captain preferred to eradicate law-breakers rather than incarcerate them, as this was cheaper for tax-payers.
After this Judoon was shot with the Time-Gun his timeline was erased and he ceased to exist. As a result, the platoon he took to Janizzar never arrived there, and the Cybock Imperium were able to escape with the gun. (COMIC: Gangland)