LONDON (Reuters) - Prince Philip, the 96-year-old husband of Britain’s Queen Elizabeth, will spend a second night in hospital on Wednesday for treatment for an infection but remains in “good spirits”, Buckingham Palace said.

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Philip, whose official title is Duke of Edinburgh, was admitted to the King Edward VII Hospital in London on Tuesday as a precautionary measure for treatment arising from a pre-existing condition.

Asked how the Duke was faring, Philip’s son and heir-to-the-throne Prince Charles told reporters: “He’s getting better.”

A palace spokesman said the Duke would remain in the private hospital in central London on Wednesday night.

Philip, who has been by the queen’s side throughout her 65 years on the throne, had been with his wife to watch horse racing at Royal Ascot, west of London, on Tuesday. His illness meant he missed the official state opening of parliament and another trip to Ascot on Wednesday.

The queen, the world’s longest-reigning living monarch who celebrated her 91st birthday in April, was instead accompanied to parliament by Charles.

“Prince Philip is in good spirits and is disappointed to be missing the State Opening of Parliament and Royal Ascot,” the palace spokesman said.

Despite his age, both the queen and her husband have continued to carry out hundreds of annual official engagements but in May Philip announced that he would retire later this year from active public life..

Outspoken, irascible and intensely private, Philip, a Greek-born former naval officer, has a reputation for brusque comments and occasional gaffes.

Elizabeth and Philip, who married at Westminster Abbey in 1947, are due to celebrate their platinum, or 70th, wedding anniversary in November.

Both have suffered some health issues in recent years. Philip underwent “an exploratory operation following abdominal investigations” in 2013.

He was also hospitalized for a bladder infection during the queen’s Diamond Jubilee celebrations the year before, and spent Christmas 2011 in hospital where he underwent an operation to clear a blocked heart artery after suffering chest pains.

The queen missed a traditional Christmas church service last year for the first time in decades because of a heavy cold and was hospitalized in March 2013 with symptoms of gastroenteritis.