The UK Government has been temporarily barred from signing a controversial agreement to transfer sovereignty of the Chagos Islands to Mauritius, after a High Court judge issued an

emergency injunction early Thursday morning.

Prime Minister Sir Keir Starmer was scheduled to participate in a virtual signing ceremony with Mauritian officials today. The deal, which would see the UK relinquish control of the British Indian Ocean Territory (BIOT) in favour of Mauritius, follows international legal rulings supporting the Mauritian claim.

Under the proposed agreement, the UK would have retained access to the strategic military base on Diego Garcia by leasing it back for 99 years. The base, jointly operated with the United States, is a crucial asset in Western defence strategy across the Indian Ocean.

The British Indian Ocean Territory, commonly referred to as the Chagos Islands, lies between Africa and Indonesia and has long been a subject of legal and geopolitical dispute.

The injunction, granted at 2:25am by Mr Justice Goose, was issued in response to a legal challenge from Bertrice Pompe, who has previously taken steps to oppose the deal. The judge ruled that the Government must not take any binding or conclusive steps toward the transfer of the territory.

A Government spokesperson commented: “We do not comment on ongoing legal cases. This deal is the right thing to protect the British people and our national security.”

Critics of the agreement, including members of the Chagossian community and some political figures, have raised concerns about national security and the exclusion of Chagossians from the negotiations. Some fear the handover could strengthen China’s influence in the region.

Despite the opposition, Government officials have defended the plan, citing safeguards within the agreement, including a reported 40-year lease extension for the base. Ministers were expected to brief Parliament following the signing.

Defence Secretary John Healey told MPs this week that Diego Garcia remains "essential to our security," adding that the Government was continuing efforts started by the previous administration.

Although the Conservatives initiated talks on the handover, they have criticised Labour’s handling of the final negotiations, with reports suggesting the deal had become politically “toxic.”

A court hearing is scheduled for 10:30am Thursday to determine the next steps.