The British premier is under pressure to quit after his Labour Party suffered election losses.
The passengers landed in the UK on Sunday and none have reported symptoms, but they will will be monitored in hospital for 72 hours.
British anti-royals have staged a ‘No Kings’ protest outside Buckingham Palace in London.
Labour and the Conservatives suffer losses at the expense of Reform across England.
The UK confirms two British cases on board a cruise ship and a suspected infection on the Tristan da Cunha island.
The patient is on the remote Atlantic island of Tristan da Cunha, which was visited by the cruise ship in April.