Prince Philip, the 96-year-old husband of Queen Elizabeth II, has been admitted to hospital as a "precautionary measure" for the treatment of an infection, Buckingham Palace said Wednesday.
Duke of Edinburgh, who is to retire from public duties later this year, was admitted to the King Edward VII hospital in central London after becoming unwell at Windsor, following his appearance at Royal Ascot.
He arrived at the hospital by car accompanied by his personal protection officer.
The Queen was accompanied to the state opening of parliament by the Prince of Wales, who is taking his father's place. She is being kept "fully informed" and will continue her plans to attend Royal Ascot following her delivery of the Queen's speech at the Houses of Parliament, the Guardian reported.
The infection arose from "a pre-existing condition", the palace said.
Earlier, Philip was admitted to hospital for a bladder infection, and for abdominal investigations and in 2011. In 2011 he was admitted to Papworth hospital where a coronary stent was fitted.
The Duke of Edinburgh will no longer carry out public engagements from the autumn of this year.