The King and Queen are due to attend a Christmas Day church service in Sandringham alongside the Prince and Princess of Wales plus other royals.
It was announced last week that the Duke of York would not attend the annual gathering after an alleged Chinese spy, named following a High Court judgement, was found to have been linked to the prince.
Wednesday's service will take place hours before the King's Christmas message airs - it will be delivered from a former hospital chapel, in a year that has seen the monarch undergo cancer treatment.
His daughter-in-law Catherine, expected to be at the service, recently marked her biggest return to royal duties after finishing chemotherapy.