The Chagos Islands is at the centre of an ongoing dispute over ownership between the UK and Mauritius. The validity of each claim is covered in another question
However, current the only use The Chagos Islands is put to is a US military base.
Since 1971, only the atoll of Diego Garcia is inhabited, and only by military and civilian contracted personnel. Since being expelled, Chagossian natives have been prevented from returning to the islands.
While the article refers to it as a joint US-UK military establishment, as far a I can see there is no significant UK component to the occupants.
Given the diplomatic issues involved, why does the UK continue to own the problem instead of handing it off to the US, to whom it already appears to have ceded control for all practical purposes.