Diego Garcia Military Base and British Indian Ocean Territory Bill

Lord Craig of Radley Excerpts

2nd reading
Tuesday 4th November 2025 Lords Chamber

[Lord Craig of Radley (CB)]

My Lords, there is general agreement about the importance to the UK’s defence security, and to the USA’s, that a stable and legal arrangement should be agreed. The 100-year and more period of this treaty makes some valiant assumptions about the longevity of the relationships between the countries involved. Governments rise and fall, and relationships shift—sometimes dramatically, sometimes on a generational rather than a centenary timeframe. Although this is far from being a well-received arrangement and treaty, it may now be increasingly difficult to change course completely. However, in following from what the noble Lord, Lord Altrincham, was saying, I have one question about the arrangements covering the payments to the Government of Mauritius.

Article 11 of the treaty says that in consideration of the agreement, which applies to the whole of the Chagos Archipelago, certain sums will be paid to Mauritius. The exchange of letters dealing with the details of these arrangements also forms part of the agreement, but the British and American interest is confined to the island and surrounding seas of Diego Garcia. In 100 years and more, there must surely be a possibility of some natural catastrophe—an earthquake or tsunami, or even a rise in ocean levels due to global warming. The runway at Diego Garcia is only a metre above today’s sea level. Any of these might make the base and/or the airfield no longer functional. Has the UK any automatic right to cease payments to Mauritius if the base is no longer usable nor capable of recovery at any reasonable cost?

Maybe the Minister will point to some section of the agreement that covers this eventuality. If it is not explicitly covered, will Mauritius still be lawfully entitled to the annual payments even if Diego Garcia is unusable? Were the UK to stop payments, would it have to be settled along the lines outlined in this agreement by arbitration and, ultimately, agreement between the respective Prime Ministers? It would not be in the UK’s national interest to be devoting scarce defence funds to a useless white elephant, but a clash over interpretation could also be damaging to our national interest.

The noble and gallant Lord, Lord Houghton of Richmond, raised this point on my behalf in the debate on 30 June. In reply, the Minister suggested:

“Like all small atoll islands, it is naturally dynamic”.


He would not speculate about future erosion but was confident that surveys overall concluded that the natural land area

“has decreased by less than a single percent over the last 50 years”.—[Official Report, 30/6/25; col. 535.]

Is that a sufficient reassurance about a natural disaster or sea levels not rising by less than a metre for the next 100 years-plus? Considerable sums might be at stake. If this eventuality is not satisfactorily covered, should it be corrected before the treaty is finally approved?