The rules will apply to all guests booked on Riviera’s group tours and cruise operations. Guests who have not had both vaccine doses will be offered a complimentary Covid test, with the test offered being "the most appropriate" at the time.

Riviera said the decision to insist on vaccination and/or a negative pre-departure test was based on feedback from a recent survey of its guests, which indicated there was strong support for additional health safeguards to guard against the spread of Covid-19.

Besides guests, Riviera’s river and ocean cruise crew, and its tour managers, will be subject to the same rules. Crew will undergo daily temperature checks and regular health screening.

Any guests who test positive for Covid-19 prior to their holiday will be able to transfer their booking to an alternative date, free of charge.

Riviera will require guests to have had both doses of the Covid vaccine, with the second dose having been administered a minimum of seven days prior to travel.

Jim Forward, Riviera’s chief commercial officer, said: "Ensuring guests’ peace of mind is a priority for us, so we’re asking everyone who travels with Riviera to have had the full Covid vaccine or presented a negative test. We can’t wait to welcome holidaymakers back so will take care of any associated costs.

"These measures, combined with our comprehensive health and safety procedures, means guests can look forward to their Riviera holiday with happiness guaranteed."

Guests who book by 30 April 30, or who make new bookings for 2022, can be changed for free up until 30 September. Covid cancellation protection is included as standard.

Guests will receive a pre-travel questionnaire, in which they must confirm their vaccination details. Guests are responsible for ensuring they comply with the vaccination and/or negative test policy.