Interesting to read that RCI wanted a letter from a UK Doctor. My wife and I contracted Covid 4 days before a cruise. Our Doctor attended to us due to our severe reaction and issued us with 'Unfit to Travel' letters. RCI refused to accept them despite the pleas on our behalf from our travel agent stating that we had not provided proof of positive tests and that the Doctors letter didn't have an NHS logo on it. No refund but eventually they said they would issue a cruise credit, still waiting on that.