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Richard Grindon's avatar

As you say this may be a moot point if the deal is truly dead.

I would like to point out a key point here and that is that since the payments are index-linked from year 14, the inflation assumption has a MASSIVE effect on the numbers.

Totalling both the Mauritius subsidy (non-index-linked) and the 'rent ' payment (index-linked) if you assume 2.2% annual inflation the total payments amount to £33.4 billion over the life of the contract. If you input 3.6% inflation (December 2025 official figure) the total payment over the life increases to £71.7bn. UK CPI average since 1989 form ONS is 2.83% and if you use this number you would get total payments equal £46.5bn.

Now of course it is true that it becomes difficult to envision what this means in current money, this is where the NPV comes in. Forget the government's wishy washy definition of NPV. Finance professionals use an interest rate to discount all the future cashflows to current value, essentially this is like saying 'how much would we have to pay upfront for the equivalent value of all these future cashflows?'. Again the discount rate has a big effect. Most logical rate to use would be 50 year gilt yield which is currently around 4.72%.

The NPV using 4.72% as the discount rate gives values of £4.26bn for the 2.2% inflation assumption, £4.76bn for the 2.83% inflation assumption, and £5.6bn for the 3.6% inflation assumption. These numbers are all much higher than the government figure of £3.5bn, probably because they have conveniently ignored the Mauritius subsidy and only focussed on the 'rent' component. Also 2.2% inflation for the UK is pretty low and unlikely realistic.

One other way to look at this would be to ask what would be the equivalent amount of index-linked gilt issuance which would equate to the liabilities of the Chagos deal? That way you just assume the same inflation and discount rate, then the NPV comes to around £10bn.

Based on the most recent UK aircraft carrier costs that buys you 3 aircraft carriers, not one as Kier Starmer compared the Chagos deal to the cost of running one aircraft carrier.

PS: I enjoy your posts. Chagos is a bit of a finance geek deal to understand fully.

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