With the weekend's Diamond Jubilee celebrations behind her, Queen Elizabeth II visited her ailing husband Prince Philip in the hospital on Wednesday where he is receiving treatment for a bladder infection.

Philip, 90, also known as the Duke of Edinburgh, was taken to King Edward VII hospital in London on Monday after falling ill. He turns 91 on Sunday.

Since being admitted, the prince's condition has "improved considerably," according to a statement on the official British Monarchy website. "The treatment of his infection continues with antibiotics. He is likely to remain in hospital over the next few days. He is in good spirits," the statement obtained by CNN said. Philip is expected to remain under observation for several days.

A former naval officer, Philip married the queen in 1947 — five years before her accession to the throne.

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