The Queen is to be made a vice admiral, reflecting the "high regard" she commands with sailors, the head of the Royal Navy has announced.
General Sir Gwyn Jenkins, First Sea Lord and Chief of Naval Staff, said the honorary role would "further enhance Her Majesty’s relationship with the service".
The appointment will be formally made when Camilla visits Devonport naval base.
There, as HMS Astute’s sponsor, she will join a ceremony marking the submarine’s first commission's end.
The honorary role, dating to the mid-1500s, includes the formal presentation of a burgee or pennant by Rear Admiral Andy Perks, head of the submarine service, recognising the Queen’s ongoing Royal Navy support.
“The honorary appointment reflects the high regard in which Her Majesty is held by all of us,” the First Sea Lord said.

Sir Gwyn, who is a Royal Marine, met Camilla on Tuesday when she was installed as an honorary freeman and liveryman of the Worshipful Company of Stationers and Newspaper Makers, an organisation associated with the Royal Marines.
“We’re super proud of Her Majesty’s role with HMS Astute, as are the crew, it really matters a lot to us as a Navy and to them as a crew that it’s the Queen’s submarine,” he said during the City of London event.
The Queen joked to him about not wanting to serve on a submarine.
The head of the Royal Navy said afterwards: “I think we would all recognise that being a submariner is a very special skill set, you have to be really committed to the role and what you do for the country.
“It can be phenomenally rewarding, it’s an amazing sense of teamwork onboard, but it’s not for everyone.”

At Devonport, the Queen and the crew will celebrate the submarine’s achievements over the past 15 years – the longest first commission of any Royal Navy submarine in history.
The hunter-killer submarine will undergo a major overhaul at Devonport naval base to allow it to continue patrols safeguarding the UK’s interests for years to come.
Commander Christopher Bate, commanding officer of HMS Astute, said the crew took enormous pride in the Queen’s sponsorship of their submarine and support for all onboard since she formally named the vessel nearly 20 years ago.
“Her Majesty the Queen has supported us from the very beginning, she has consistently shown a deep commitment to all aspects of our work,” he said.
“Her continued engagement with our activities and achievements over the years has meant a great deal to us.”
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