Rules have changed once again and latest update is as of August 10. Now they have added "medically observed" to the PCR test. Antigen test can be self-administered.
Unless otherwise communicated, all guests ages five and older must take a viral COVID-19 self-administered Antigen or medically observed PCR test within three days prior to embarkation on the ship. This can be done at any time in the three days before the day of embarkation. Guests no longer need to provide a test certificate, however they will be asked to confirm that the test has been taken, with a negative result, as part of the pre-boarding health declaration at the cruise terminal/airport. Guests under five years of age are exempt from pre-cruise testing. (Please note that these updated guidelines apply to the UK but not to the U.S., Canada or EU).