Diego Garcia and the Chagos Islands: the deal and what it costs

🌴 How to read the Chagos figures ✕

So have we given the islands away or not?

No. A treaty was signed on 22 May 2025, and signing is not the end of the process — a treaty that needs a change in British law does not take effect until Parliament passes that law. The Bill got through the Commons, the Lords amended it in January 2026, and the Commons overturned those amendments on 20 January, dividing three times. Then it needed to go back to the Lords one last time, and that stage was listed as "date to be announced" and never scheduled. On 13 April 2026 ministers said the Bill could not finish, because the United States would not agree the updated 1966 exchange of notes that ratification depends on. It was not in the King's Speech in May 2026. No sovereignty has moved, no money has changed hands, and the base still operates under the arrangements Britain and America made in 1966, which run to 30 December 2036.

Is it dead, then?

The government will not say. On 30 July 2026 three separate written questions — including one asking simply whether it remains policy to transfer the territory — all got the same sentence back: that ministers "will continue to work with the US and Mauritius to find a way forward". On 1 September 2026 the Commons was told the United States "must be content with the agreement before we proceed in ratifying the treaty". So: signed, unratified, unfunded, no bill before Parliament, and not withdrawn. Treat this section of the tile as the part most likely to be out of date.

Why the same deal cost £3.4 billion and £35 billion

Because those are two ways of adding up the same instalments, and both were honest. The £3.4bn is a net present value: future payments discounted back to today's money at the Treasury's standard Green Book rates, on the reasoning that a pound payable in 2124 is not a pound now. The £34.7bn is what the cheques would total in cash. Between them, about £10bn is the figure if you adjust for inflation but do not discount. The head of the UK Statistics Authority did not say the government's number was wrong; he said it should not have been called "the net overall cost" without saying it had been discounted, and he noted the Office for Budget Responsibility thought the discount rate reasonable for valuing a lease. Higher totals have been quoted using different inflation and discount assumptions; the tile draws the three whose method is published, because a total you cannot check the workings of is not a fact.

An advisory opinion is not a court order — so why did it matter?

It is the heart of the disagreement. The International Court of Justice's 2019 opinion was advisory: it bound nobody, and critics say the government treated advice as a verdict. The government's answer is that the 2021 tribunal case showed where advice leads. There, a Law of the Sea chamber deciding a boundary between Mauritius and the Maldives — a case Britain was not party to — treated the International Court's findings as settling the legal status of the archipelago, and did it without Britain in the room. Ministers concluded a binding ruling was a matter of time, and that meanwhile the base's ability to hold radio spectrum, postal codes and fishing rights was being picked at through UN agencies. The strongest reply is that since 1998 Britain has formally excluded disputes about military activities from the compulsory jurisdiction of those tribunals — though that is a shield the tribunal itself decides whether to accept, and it does nothing about the International Court or the General Assembly. Whether all this was prudence or surrender is exactly what the argument is about, and the tile gives both sides their own words.

What "British Indian Ocean Territory" is

It is one of the fourteen British Overseas Territories — British sovereign land that is not part of the United Kingdom. Unlike the Falklands or Gibraltar it has no settled civilian population, because the people who lived there were removed between 1968 and 1973. That absence works both ways in the argument: the government says there is no population whose self-determination could be at stake, so the Falklands and Gibraltar are not a precedent; Chagossians say the absence is precisely the wrong being argued over, and that they were never asked. In February 2026 four Chagossian men landed on Île du Coin and refused to leave, and in March a court there struck down the rule that had kept them out — an order now suspended while the government appeals.

Why the tile does not say what "the Chagossians want"

Because they do not agree, and pretending otherwise would be the site putting words in people's mouths. The Chagos Refugees Group in Mauritius welcomed the signing; Chagossian Voices opposed it and wants a right of return that includes Diego Garcia itself, which no version of the deal offered. Both are quoted. What is not in dispute is that no Chagossian organisation was a party to the negotiation, that UN human rights experts said so publicly in June 2025, and that most of those who answered a Lords committee survey lacked confidence in the proposed trust fund.

What we left out on purpose, and what we took out

Whether the deal was right. That is a judgement about sovereignty, international law and an ally's goodwill, and it is not ours to make on your behalf. We also took several things out after a second check: two higher cost totals whose workings we could not obtain, a claim about how many supply ships sit in the lagoon, a comparison with what France pays for a base elsewhere, and a count of Gulf war bombing missions — all of them plausible, none of them traceable to a source we could open. Where a figure is missing from this tile it is usually because of that, and not because it was inconvenient.

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