For the first time, the High Court has fully examined the law concerning a public inquiry’s ability to compel in-person attendance of a witness living overseas. In this blog, civil litigation partner Helen Stone analyses its ruling, and assesses its significance.

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In June 2026 the Divisional Court handed down its decision in R (on the application of UCPI Designated Lawyer Officers Core Participant Group) v Sir John Mitting (sitting as Chairman of the Undercover Policing Inquiry) (‘UCPI’) [2026] EWHC 1394 [HS1][HS1] (Admin).

The application concerned the power of this public inquiry to compel witness attendance in circumstances where that witness lives abroad.

Despite several other public inquiries having made statements and indications about this issue prior to the challenge before the court, the court stated it understood that this was the first time that this extra-territoriality issue had received full argument before a court.

The court found against the applicant and ruled that that Chair of this public inquiry had the power to issue a notice under section 21 of the Inquiries Act 2005 (‘the 2005 Act’) for the witness to appear at the Inquiry.

Judicial review of s.21 notice compelling inquiry attendance

The Undercover Policing Inquiry (UCPI) was set up in 2015 by then Home Secretary Theresa May under the Inquiries Act 2005. It was designed to “inquire into and report on undercover police operations conducted by English and Welsh police forces since 1968…”.

The application for judicial review was brought by the UCPI Designated Lawyer Officers Core Participant Group (‘the Claimant’) who represent a number of former Metropolitan Police Service (MPS) personnel, including an officer known as HN86.

The challenge was brought in relation to the decision of the Chair of the Inquiry, Sir John Mitting (‘the Defendant’), to issue a notice under s.21 of the 2005 Act compelling HN86 to attend in London to give oral evidence. At the time the notice was served HN86 was resident abroad. It was asserted that the Defendant did not have the power to compel attendance.

A second ground of challenge (which the Court was clear it considered was ‘very much subordinate to the first ground’) was whether there was procedural unfairness in connection with the issue of the notice.

How the Inquiries Act 2005 treats notices to compel attendance

The key relevant provisions of the 2005 Act to this application are:

• s.21(1)(a) which provides that the Chair of an Inquiry may “by notice require a person to attend at a time and place stated in the notice to give evidence”.

• s.35(1) which states that “A person is guilty of an offence if he fails without reasonable excuse to do anything that he is required to do by a notice under section 21.”

The section then sets out that an offence under subsection (1) may be instituted by a chairman, and that a person guilty of an offence under this section is liable on summary conviction to a fine not exceeding level three on the standard scale or to imprisonment for a term not exceeding the relevant maximum, or both, the relevant maximum in England and Wales being 51 weeks.

The Claimant’s position was that, as HN86 resided out of the jurisdiction, the Chair did not have the power to issue a s.21 notice to an individual overseas, and therefore the s.21 notice the Chair had sent was unlawful.

The Divisional Court’s decision

The court found against the application on both grounds.

In its judgment, the court noted that in a number of other public inquiries including The Al Sweady Inquiry, The Litvinenko Inquiry, the Grenfell Tower Inquiry, and the Manchester Arena Inquiry, the territorial reach of s.21 notices (or at least the ability to enforce them) had been considered. The judgment briefly addressed how these had been approached.

However, the court found that whilst the statements and indications from those inquiries generally favoured the Claimant’s case, it understood the claim before the court to be the first time a full argument had been heard. The court stated that what appeared to have happened in other public inquiries was of limited assistance in this case.

Following consideration of the jurisdiction of international law, the presumption of statutory interpretation in domestic law, the ‘effects doctrine’ and the ‘substantial measure’ test in domestic law, Sections 35 and 36 of the 2005 Act, and analysis of the position, the court found that the Chair had the power to issue a s.21 notice to a witness who is overseas.

The court stated that the ‘nub of the problem’ in the case was that:

“…The purpose of a section 21 notice is to require the witness to attend the inquiry on a certain date at a certain time. The failure to attend at the due time is an offence of omission.  Up to that moment, it is still possible in law for the witness to comply and so avoid criminal liability.

“The fact that the witness happens to be resident in another country outside the UK does not alter the nature of that offence of omission at that time and place.  In principle, there is no material difference between that scenario and the one where the witness is abroad on holiday or business: in both scenarios the witness is outside the territory of the UK at the relevant time, when they should be in London at the inquiry.

“We consider that, in neither scenario, is this in substance an exercise of extra-territorial jurisdiction by the UK Parliament.  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.” (paragraphs 86-87)

The court went on to say that:

“In our view, the correct analysis of the present legislative context is that it is not in truth an exercise of extra-territorial jurisdiction but rather is an example of the “substantial measure” doctrine to which we have referred above. The substantial measure of the activities which are made criminal by section 35 takes place in the UK.” (paragraph 89)

Analysis of the Court’s decision

It is notable that the court was clear that it did not consider that the fact that HN86 was (and remains) a British national to be a crucial factor.

Nor did it consider that the principled answer to the issue at stake would differ if the relevant witness were a foreign national. This is because the court stated that it did not consider that this was a context in which the UK needs to rely on the nationality principle since it is not seeking to exercise prescriptive jurisdiction outside its territory.

By way of analogy, the court gave the example of a public inquiry considering something that had happened in a NHS hospital, in which an important witness may be a foreign national – perhaps a retired doctor or nurse – who was now resident in another country.

In this hypothetical circumstance, the court stated, it is “entirely reasonable to consider” that, in enacting s.21 of the 2005 Act, Parliament “must have intended that it should be lawful for the chairman of the inquiry to issue a section 21 notice requiring that person to give evidence at the inquiry in the UK.” (paragraph 104(iv)).

The court made it clear that it considered there may be practical considerations which could oblige an inquiry to take steps to sensitively meet the reasonable concerns of an extra-territorial witness. It gave as examples a witness with a medical condition which meant they could not attend in person.

In these circumstances, the court stated, an inquiry might consider if such a witness might give evidence remotely and that, if they did travel to the UK, reasonable travel and accommodation expenses be paid by the inquiry.

However, the court was clear that it does not consider such practical considerations should mean that a witness can defy a notice which requires their evidence to be given.

The current position

At the time of writing, it is not known if the decision of the Court will be challenged by the Claimant. However, the current position is that the Divisional Court has found that the Chair of the UCPI – and therefore all Chairs of public inquiries – has the power, under s.21 of the 2005 Act, to issue a notice to a witness who is abroad to compel them to give evidence, such that they risk committing a criminal offence if they do not, in fact, appear at the date and time given on the notice.

Whether that has a practical effect is likely to be case specific. If the person who receives the s.21 notice intends never to come to the UK they may be less likely to be concerned about ignoring such a notice than someone who does intend to do so.

In any event, the court’s judgment is clear that a witness being overseas is no bar to any public inquiry Chair exercising the power to issue a s.21 notice, and to potentially apply to institute criminal proceedings should the witness fail to comply.

This is therefore an issue which Chairs of public inquiries should carefully consider, as well as being one on which Core Participants and potential witnesses will need to be advised.