Diego Garcia Military Base and British Indian Ocean Territory Bill — Will write letters: Letter from Lord Coaker to Baroness Goldie and Lord Lilley regarding how the Government has taken account of the Pelindaba Treaty in relation to the UK-Mauritius Agreement concerning the Chagos Archipelago, as discussed during the Report stage.

THE LORD COAKER
MINISTER OF STATE IN THE HOUSE OF LORDS

Baroness Goldie
House of Lords

MINISTRY OF DEFENCE
FLOOR 5 ZONE B MAIN BUILDING
WHITEHALL LONDON SW1A 2HB

Telephone020 7218 9000 (Switchboard)

MSU 4-2-7-4 8 January 2026

Dear Baroness Goldie,
I would like to express my gratitude for your continued constructive engagement with
the Diego Garcia Military Base and British Indian Ocean Territory Bill. I am writing
following our discussion on Monday at Report Stage, where you asked for further detail
on how the Government has taken account of the Pelindaba Treaty in relation to the
UK-Mauritius Agreement concerning the Chagos Archipelago.
As you have noted from your own study, while the UK is not a Party to the Pelindaba
Treaty, it is a Party to Protocols I and II. Protocols I and II of the Pelindaba Treaty place
obligations on the five nuclear -weapon States recognised by the Non -Proliferation
Treaty (China, France, Russia, UK and US).
• Protocol I prohibits these states from threatening or using a nuclear explosive
device against any Party to the Treaty or territory within the zone.
• Protocol II prohibits the testing of any nuclear explosive device anywhere within
the zone.
Both the UK and Mauritius are satisfied that our existing international obligations are
fully compatible with the UK-Mauritius Agreement.
Annex IV of the Pelindaba Treaty requires that a Party which considers another Party,
or that a Party to Protocol II , is in breach of its obligations under the Treaty must first
raise the matter with the Party concerned. Neither the UK nor Mauritius have received
such a complaint.
All operations on Diego Garcia will continue to comply with applicable international
law. The security provisions we have secured as part of the Agreement ensure that
the UK has full operational control over Diego Garcia, including unrestricted access to
and use of the military base.
In the unlikely circumstance that Mauritius has concerns about action taken from the
base on Diego Garcia, it can raise them in the Joint Commission as provided for under
Article 14 of the Treaty and there can be further consultations and negotiations right
up to Prime Ministerial level. A difference of opinion on the legal basis for UK activity
is not a ground for termination of the Treaty, and could not impact UK or US operational
decisions once the treaty has entered into force.

I wish to also draw your attention Article 7(3) of the Treaty, which confirms that the UK
and Mauritius agree that nothing in the Agreement shall subject either country to any
obligation under a treaty to which it is not a party or which is not applicable to the
territory covered by this Agreement.
It is important to stress that t he UK -Mauritius Agreement does not undermine the
Pelindaba Treaty or other nuclear -weapon-free zone treaties – including the one to
which Australia, our AUKUS partner, is Party – nor does it set a precedent for other
countries. The United Kingdom remains supportive of the objectives of the Pelindaba
Treaty.
Regarding the presence of nuclear weapons, the UK maintains its long-standing policy
of neither confirming nor denying their location.
I hope that this response proves helpful to you. I have copied this letter to the noble
Lord Lilley and I will also place a copy in the Library of the House.

Yours sincerely,

THE LORD COAKER