Can a statutory public inquiry compel an overseas witness to attend an inquiry hearing?

On 9 June 2026 judgment was handed down in R. (on the application of UCPI Designated Lawyer Officers Core Participant Group) v Mitting ([2026] EWHC 1394 (Admin)), dismissing an application for judicial review of the decision by the Chair of the Undercover Policing Inquiry ("the Inquiry"), Sir John Mitting, to issue a notice under section 21 of the Inquiries Act 2005 ("the Act") to compel a witness living abroad to attend the Inquiry hearings in London.

Factual background

The witness has been granted anonymity by the Inquiry and is known by the cipher HN86. He is considered by the Chair to be "a witness of particular importance", having served in the Special Demonstration Squad ("SDS") in the late 1970s and early 1980s as an undercover officer, and from 1990 to 1994 as a manager. The SDS is one of two main undercover policing units being investigated by the Inquiry.

Following correspondence between his representatives and the Inquiry, HN86 confirmed that he did not agree to give oral evidence, either in person or remotely. Although his representatives informed the Inquiry that HN86 was unwell, they were clear that they were not applying for him to be excused on medical grounds; the correspondence simply stated that HN86 "is not agreeing to return to the jurisdiction to give oral evidence and has specifically stated that he does not want to give evidence either remotely or in private". As the Court put it, "'implicit in this response is the assertion that he could not be compelled by [the Chair] to return to the UK".

HN86 was subsequently served with a section 21 notice requiring attendance in person at the Inquiry hearings, underscoring the "exceptionally compelling reasons" for requiring HN86's oral evidence. Under section 35(1) of the Act, failure to comply with a section 21 notice without reasonable excuse is a criminal offence.

HN86's representatives requested withdrawal of the notice on the basis that it was unlawful as the Inquiry did not have the power to issue section 21 notices to witnesses overseas. The Inquiry maintained its position that the notice was lawfully issued.

Judicial review grounds

A claim for judicial review of the Chair's decision to issue a section 21 notice was subsequently brought by the UCPI Designated Lawyer Officers Core Participant Group ("the Claimant"), who represent various former officers involved in the Inquiry, including HN86.

As a second, subsidiary ground of challenge, the Claimant also alleged procedural unfairness in the way in which the section 21 notice was issued, arguing that the notice came as a "bolt from the blue" and that, had HN86 been given more warning, he could have provided representations as to his health and his non-compellability from overseas.

The previously understood position

The Claimant highlighted various examples of previous Inquiry Chairs appearing to have understood that they did not have power to compel overseas witnesses to give evidence, as follows:

• The Al Sweady Inquiry report at volume 1, paragraph 1.137: "Although s.21 Notices were served on these witnesses [now residing overseas], in order to compel them to attend a particular venue to give evidence on a particular date, the Notice has no reach overseas…"
• The Litvinenko Inquiry report at paragraph 4.81: "Both men gave evidence to the Inquiry voluntarily – since they both live out of the jurisdiction, I could not have compelled them to give evidence…"
• The Grenfell Tower Inquiry report at volume 2, paragraph 16.16: "The position in relation to [four foreign witnesses] was rather different because, having taken legal advice, the chairman was satisfied that no legal mechanism existed to compel their attendance in this country."
• The Manchester Arena Inquiry report at volume 3, paragraph 25.23: "A section 21 notice will apply to any individual or organisation in the UK, but not beyond."

It was also noted that in the separate but analogous context of inquests, HM Chief Coroner's Guidance for Coroners on the Bench states (chapter 13, paragraph 62) that there is "no power to compel evidence from a person who is outside the jurisdiction of England and Wales".

However, the Court was clear that this was the first time the issue had received full argument before a court, meaning that "what appears to have happened in other public inquiries, for example, on the basis of legal advice which we have not seen, is only of limited assistance".

Argument

The Claimant relied on the established presumptions that Acts of Parliament do not have extra-territorial effect, and that statutory provisions which create criminal offences do not criminalise conduct committed outside the UK. It was also noted that there was nothing in the language of section 21 which indicated a specific intention for the provision to have extra-territorial effect.

Both parties made arguments as to practicality. The Claimant argued that enforcing the section 21 notice against HN86 would be impractical as the alleged criminality did not take place in England and Wales and the section 35 offence is not an extradition offence under the Extradition Act 2003. The Chair accepted the practical difficulties but argued the threat of enforcement could still apply coercive pressure and incentivise voluntary attendance.

The Chair noted the distinction in international law between prescriptive and enforcement jurisdiction. Prescriptive jurisdiction is a state's authority to apply its domestic laws, whereas enforcement jurisdiction is the physical enforcement of a state's laws. Prescriptive jurisdiction can be exercised extra-territorially if the state can rely on a rule of international law to do so, but enforcement jurisdiction is always territorial. Put simply: a state can in some circumstances consider its laws to apply to people abroad, but it cannot, for example, use its own police to arrest someone overseas.

One of the established circumstances in which prescriptive jurisdiction can be exercised extra-territorially is the 'nationality' or 'active personality' principle: a state can criminalise conduct by its own nationals overseas, so long as this does not interfere with the affairs of the overseas state. HN86 is a British national, despite having resided overseas for many years. It was therefore argued by the Chair that extending criminal liability to HN86, but not seeking to enforce it, was a legitimate exercise of extra-territorial prescriptive jurisdiction and did not violate any principles of international law.

The decision

However, the line of argument which was ultimately successful for the Chair did not involve international law at all. The Chair argued that the section 35 offence is one of omission, and that the omission – failure to attend the hearing – takes place in the UK. It follows that the section 35 offence is made out in the UK, wherever the witness may be, and so issuing a section 21 notice to an overseas witness is not an exercise of extra-territorial jurisdiction. As the Court put it: "the offence, or at least a substantial part of it, takes place in the territory of the UK: where there should be a witness, there is an empty chair".

The Chair did not therefore need to rely on the nationality principle set out above. Indeed, the judgment goes on to explain that the position would be the same even if HN86 had not been a British national, giving the example of a retired NHS doctor or nurse who was now resident overseas.

Regarding the second ground of challenge, the Court summarised the correspondence between the Inquiry and the Claimant regarding HN86's attendance at the Inquiry and found that the Chair had not acted unfairly; the Claimant had been given sufficient notice of the Chair's intention to issue a section 21 notice, and the Inquiry had repeatedly offered to facilitate HN86 giving evidence remotely.

The application for judicial review was therefore dismissed in its entirety.

Significance

The decision reverses the previously understood position that public inquiries could not compel overseas witnesses to attend. It will provide clear guidance for any current and future Inquiry Chairs who may find themselves in the position of requiring evidence, whether oral or documentary, from a reluctant overseas witness.

More broadly, the judgment provides a useful restatement of the key role played by public inquiries in investigating matters of public concern involving the state. In differentiating this application from previous jurisprudence involving litigation between private individuals, the Court emphasised what it referred to as the "very strong public interest in ensuring that public inquiries have access to the information necessary to ensure their efficacy". This reasoning could in theory be applied to other questions involving the limits of powers enjoyed by Inquiry Chairs.

TLT’s Public Inquiries, Inquests and Public Law team has significant experience working on statutory and non-statutory inquiries and independent reviews. Mark Perry, Partner at TLT, is appointed as Solicitor to the Undercover Policing Inquiry and is supported by a team of TLT lawyers working in partnership with GLD.

To discuss the subject matter of this article further or for assistance with public inquiries in general, reach out to our team of expert lawyers.

Authors: James Wilson, Jennifer Parr and Sophie Holmes

This publication is intended for general guidance and represents our understanding of the relevant law and practice as at August 2026.  For more information see our terms & conditions.