Why did the government sign the Chagos deal now?

In a fast-moving world, suffused by conflict and political uncertainty, it might seem odd for the UK government to surrender sovereign British territory in a distant sea.

Indeed, the government's critics go further and say the decision to give up a key strategic foothold in the Indian Ocean is a dangerous weakening of UK security.

So why has the government handed the Chagos Islands to Mauritius, a nation some thousand miles away?

The answer has a legal origin and a practical conclusion.