Page "Security clearance" Paragraph 25

Clearance is checked at four levels, depending on the classification of materials that can be accessed — Counter-Terrorist Check ( CTC ), Baseline Check ( BC ), Security Check ( SC ), and Developed Vetting ( DV ).

Security Check allows an individual long-term unsupervised access to protectively-marked SECRET material, whilst for TOP SECRET Developed Vetting is required.

All Officers and some specialist trades within the British Armed Forces are cleared to SC to enable them to carry out their jobs.

Further to this, in the Royal Corps of Signals, all soldiers holding the appointment Foreman of Signals or Yeoman of Signals, and also certain appointments within the Intelligence Corps are DV cleared.

Those with security clearance are commonly required to sign a statement to the effect that they agree to abide by the restrictions of the Official Secrets Act.

This is popularly referred to as " signing the Official Secrets Act ".

Signing this has no effect on which actions are legal, as the act is a law, not a contract, and individuals are bound by it whether or not they have signed it.

Signing it is intended more as a reminder to the person that they are under such obligations.

To this end, it is common to sign this statement both before and after a period of employment that involves access to secrets.