Queen Elizabeth II, 90, and her husband Prince Philip, 95, have delayed their Christmas travel plans because they are both suffering from heavy colds, Buckingham Palace says.
Elizabeth, the world's longest-reigning living monarch, and Philip had been due on Wednesday (local time) to catch a train from London to their Sandringham country residence in Norfolk, eastern England, where they traditionally spend Christmas.
"The Queen and The Duke of Edinburgh have heavy colds, and so have decided not to travel to Sandringham today," the royal office said in a short statement.
The couple, who have been married for 69 years, were well enough on Tuesday to host members of the royal family for a lunch at Buckingham Palace in London attended by heir to the throne, Charles, his son Prince William, and grandson Prince George, third in line to succeed the Queen.
After six decades on the throne, the Queen has cut back on international tours but still regularly performs official duties around Britain, although she said on Tuesday she would reduce the number of her patronages.
Although Elizabeth's father, George VI, died at the relatively young age of 56, her mother, who was known as Queen Elizabeth the Queen Mother, lived until 101 and was still appearing in public almost up until her death in 2002.
Both the Queen and Prince Philip's good health has allowed them to remain very much in the public eye, despite their age.
The Times reported on Wednesday that Philip carried out more public engagements last year than did his grandsons Princes William and Harry, and William's wife Kate combined.