The Royal Navy Colonial Defence Authority was the body which governed all issues related to the defence of Colonial Worlds by the Royal Navy between 2167 and 2261. It was operated from CDA Cheltenham throughout it's lifetime.
In 2261 it was announced that the Colonial Defence Authority's role would be merged into the Colonial Emergency Defence Command Headquarters.
The CDA maintained a small security force of 2000 men which could be attached to a Royal Navy ship in times of war. It also housed a large command and control centre with a direct link to the Defence Mainframe.
The CDA also had the authority to dispatch Royal Navy vessels when the need arises, an example of an event which required the assignment of forces by the Colonial Defence Authority was the Harvest Ambush