So the official page from Royal Caribbean does not include British Citizens on the list of visa free entries to Vietnam (from this page, and calling them to confirm: https://www.royalcaribbean.com/faq/questions/international-ports-travel-considerations)
However I have been to Vietnam several times visa free, and the gov.uk says the following: "Until 30 June 2021, ‘British Citizen’ passport holders travelling for tourism or business can enter Vietnam for up to a maximum of 15 days (inclusive of dates of entry and exit) without a visa." (https://www.gov.uk/foreign-travel-advice/vietn
