[nomadking]

Originally Posted by Dingbat

So when Truss and Cleverly started the ball rolling on the agreement to hand over Chagos in 2022, they must of course have realised that treaty existed?

Or were they equally incompetent?

Not sure giving up sovereignty was planned at that point.
Link

...
the UK and Mauritius have decided to begin negotiations on the exercise of sovereignty over the British Indian Ocean Territory (BIOT)/Chagos archipelago.
...
We will seek to strengthen significantly our co-operation on Indian ocean security, maritime security and marine protection, conservation of the environment, climate change and respect for human rights, and on tackling illegal migration, illegal fishing, drugs and arms trafficking, as well as bilateral co-operation on a range of other issues.

If sovereignty was being given up, no point in discussing those other matters.
Link

On 3 October 2024, the UK and Mauritius issued a joint statement, affirming Mauritius' sovereignty over the Chagos Archipelago while granting the UK continued control over Diego Garcia for 99 years. This agreement implicitly indicates that the UK will maintain sovereignty over Diego Garcia, which hosts a critical military base. Additionally, provisions for Chagossians, regional security, and environmental cooperation are included, strengthening bilateral ties between the two nations.[63][64]
In his October 2024 statement on the Chagos Islands, Foreign Secretary David Lammy discussed the contested status of the territory and the UK-US military base.