The U.K. says it has reached a "historic" deal to cede the Chagos Archipelago in the Indian Ocean to the Republic of Mauritius, thus surrendering the final colony of Britain's once-sprawling African empire.

The U.K. has agreed to hand sovereignty of the long-contested Chagos Islands, an archipelago of more than 60 islands in the Indian Ocean, to Mauritius, in a deal to secure the future of a strategically important U.