The Queen will spend another day in hospital as she continues to battle the stomach virus gastroenteritis, reports say.
Her Majesty, 86, is under the care of doctors at King Edward VII Hospital in London, the same private hospital which treated Kate Middleton for acute morning sickness in December.
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The royal, in hospital for the first time in ten years, has cancelled all engagements including a planned trip to Rome with the Duke of Edinburgh.
On Monday, Prince Philip was due to visit the Royal Thames Yacht Club in Knightsbridge, which would have made a visit to his wife in the King Edward VII Hospital likely following the engagement.
A spokesman for the Queen insisted the monarch was in "good spirits" and that her stay in hospital was "a precautionary measure".
He added: "She was not taken into hospital immediately after feeling the symptoms. This is simply to enable doctors to better assess her."
News of the Queen's illness came on Saturday when she was forced to cancel a visit to the Welsh city of Swansea where she was due to mark St David's Day.