The Queen is believed to be planning to mark her 90th birthday with a family cruise around the Western Isles.
The ship rumoured to be earmarked for the jaunt is the same one the monarch used to celebrate her 80th birthday – the Hebridean Princess.
The ship’s calendar for next year shows only one cruise “sold out” – and that is the nine-night Footloose in the Far North sailing which starts from Invergordon on July 30 and finishes at Scrabster.
A spokeswoman for the ship’s operators, Hebridean Island Cruises, said places on that particular voyage had been snapped up by the “general public”.
But she declined to comment on whether the vessel had been privately chartered for a holiday next year.
The Queen loves to relive her annual jaunt aboard the Royal Yacht Britannia around the Western Isles.
Britannia made her last cruise in 1996 before being decommissioned the following year.
The Queen memorably shed a tear at the 1997 decommissioning ceremony.
The Hebridean Princess, which was a car ferry for 25 years, was turned into a luxury cruise ship in 1989.
The 200ft, 51-year-old vessel, which has 30 cabins, started life as the Caledonian MacBrayne car ferry and Royal Mail Ship, initially RMS then MV Columba.
She was based in Oban for the first 25 years of her life, carrying up to 600 passengers, and 50 cars, between the Scottish islands.
Hebridean Island Cruises, the only cruise line in the world to be granted a Royal Warrant by the Queen, will also be attending the Royal Warrant Holders Association trade fair and showcase on November 10 at St James’s Palace.
A Buckingham Palace spokesman said: “We would not comment on the private time of the Queen or members of the royal family.”