Britain and Mauritius are mounting a last-minute effort to finalise a deal over the sovereignty of the Chagos Islands — and a crucial UK-US military base — as concerns grow that the inauguration of Donald Trump next week could throw it into doubt.

The UK is willing to front-load the first seven years of annual payments to Mauritius as part of a sweetened deal ceding sovereignty of the Chagos archipelago to the Indian ocean nation.