Useful Definitions

Code of Practice

A Code of Practice provides guidance to public authorities on the procedures to be followed when they use investigatory powers. A public authority must have due regard to any guidance in the relevant Code of Practice. In general, there are separate Codes of Practice available for each power. These are available on the GOV.UK website.

Collateral intrusion

Collateral intrusion is the interference with the privacy of individuals who are neither the targets of the operation nor of intelligence interest. An example of this would be the unintentional recording of background conversation of passers-by alongside the speech of the target. Additional intrusion to the privacy of the passers-by would have taken place – this is collateral intrusion.

We expect public authorities proactively to assess the possible extent of collateral intrusion in any proposed activity and, where possible, take reasonable steps to prevent this.

Covert surveillance

Surveillance is covert if it is carried out in a manner that ensures the subject of the surveillance is unaware that it is or may be taking place.

Surveillance includes monitoring, observing or listening to people, their movements, conversations or other activities and communications. It may be conducted with or without the assistance of a surveillance device and includes the recording of any information obtained.


Public authorities must have authorisation to use the most intrusive investigatory powers. Authorities will therefore submit applications for the use of investigatory powers to a Secretary of State or a senior officer; this decision is then reviewed and authorised by one of our Judicial Commissioners – only with authorisation from one of our Commissioners can a warrant be issued.

This is the double-lock process. It ensures a two-stage approval for the use of investigatory powers.


A modification is a change to a warrant authorising the use investigatory powers. It is requested after the warrant has been issued. A modification to a warrant could be, for example, adding an additional individual so that their communications can be lawfully intercepted.

National Security Notice

Under section 252 of the Investigatory Powers Act 2016, a Secretary of State, with approval from a Judicial Commissioner, can issue a National Security Notice to direct a UK telecommunications operator to act in the interests of national security. This covers actions to assist the security and intelligence agencies, which may additionally be authorised under a warrant. National Security Notices could, for example, ask a company to provide access to a particular facility.

Relevant error

A “relevant error” is an error made by a public authority when carrying out activity overseen by IPCO. A relevant error is defined in section 231(9) of the Investigatory Powers Act.

Serious error

Section 231(2) of the Investigatory Powers Act defines a serious error as one where significant prejudice or harm has been caused to an individual as a result of a relevant error.

Technical Capability Notices

Under section 253 of the Investigatory Powers Act 2016, the Secretary of State, with approval from a Judicial Commissioner, may issue a Technical Capability Notice to require telecommunications or postal operators to ensure they are able to provide assistance with the acquisition of communications data, interception and equipment interference.

After a Technical Capability Notice has been issued and implemented, a company can act quickly and securely when a warrant is authorised.

Thematic warrants

Thematic warrants are warrants that have more than one subject. There are two types of thematic warrant:

  • The first individually names/describes all the subjects. Any additional subjects can only be added by a “modification” – for law enforcement agencies, a modification requires prior approval by a Judicial Commissioner, or retrospective approval if the modification is urgent.
  • The second does not individually name/describe each subject, because this is not reasonably practicable. For this type of warrant, the authority does not need to add subjects by modification: action may be taken against a person, organisation or piece of equipment (depending on the type of thematic warrant) included within the general description of the subjects.

The Principles

“The Principles relating to the detention and interviewing of detainees overseas and the passing and the receipt of intelligence relating to detainees” are more commonly referred to as “The Principles”. These are published by the Cabinet Office and apply to the intelligence services, the National Crime Agency, the Metropolitan Police Service, the Armed Forces and the Ministry of Defence.

The Principles are intended to ensure that the treatment of detainees overseas, and the use of intelligence on detainees, is consistent with the UK’s human rights and international law obligations.

The document seeks to provide clear guidance to staff often operating in legally complex and challenging circumstances. The Principles came into force on 1 January 2020.

Urgency provisions

Urgency provisions are the conditions under which, due to time-sensitive operational reasons (such as an imminent threat to life), legislation permits a departure from the normal authorisation process. For an investigatory power that typically needs to be subject to the “double-lock”, the urgency provisions mean this can be used without a Judicial Commissioner’s approval in advance.

If an urgency provision is used, the person who decided to issue a warrant to use the investigatory power must inform a Judicial Commissioner that it has been issued and the power has been used. A Judicial Commissioner must then either:

a) decide whether to approve the decision to issue the warrant and notify the authority of the Judicial Commissioner’s decision; or

b) decide to refuse to approve the decision, in which case activity under the warrant must stop and the Commissioner may direct that any information obtained under the urgent warrant be destroyed.

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