The Service

The Security Service was a secret organisation that protected the British Empire. It was run by the Star Chamber.

By the 18th century, the Security Service had been in existence for centuries. It had formerly been called the Secret Service. In 1762, Sabbath faced his final initiation by the Security Service. He was rescued by the Council of Eight. (PROSE: The Adventuress of Henrietta Street)

Alternate timeline
In an alternate timeline created by the Oracle, the twenty-one-year-old Sabbath faced his final initiation into the Security Service in 1732. While the Eighth Doctor was in that timeline in 2003, he was manipulated by Security Service agent Hannah Baxter to help her uncover leaders in the government resistance movement. (PROSE: The Domino Effect)