British troops have landed in Port Sudan on a reconnaissance mission as officials scramble to work out an evacuation plan for the 4,000 UK citizens trapped in Sudan, where violence is raging in the capital, Khartoum.

Rishi Sunak is considering how to best extract UK nationals from Sudan. One option is to increase Royal Air Force flights from a British airbase in Cyprus to a Sudanese military airfield outside the capital.

Whitehall sources told Sky News that a British warship – HMS Lancaster – is in the area, and could help with evacuations.