17:55 Update: Queen leaves hospital after 45 minute visit.
17:40 Prince Andrew has just arrived at Philip's hospital, joining the Queen at her husband's bedside.
17:10 update: The Queen has just arrived at the central London hospital where Prince Philip is being treated for a bladder infection.
The Queen's visit came just hours after she finished her final engagement of the central Jubilee weekend, a lunch with leaders of the commonwealth.
The Queen was pictured smiling broadly earlier today as she attended a Diamond Jubilee lunch for Commonwealth leaders and their partners today, suggesting that her husband was doing well. A Palace spokesperson said that her husband, the Duke of Edinburgh was "in good spirits", responding well to antibiotic treatment for his bladder infection and 'has improved considerably since coming into hospital on Monday'.
Lord Robert Salisbury, the aristocrat who organized the riverboat pageant, and who has been criticized for not sufficiently weatherproofing the Royal barge, launched a tentative defense of his pageant today, telling the London Evening Standard, "He stood up all the way and seemed to be enjoying it enormously. Fingers crossed, let's hope he's alright. I took some comfort from reports in the press that we couldn't have given him the infection. Let's hope all is well because he showed every sign of enthusiasm and enjoyment…I'd hate to carry the can for anything worse."
The Duke missed the bulk of the Queen's Diamond Jubilee celebrations after being taken to London's King Edward VII Hospital as a "precautionary measure", following the cold and wet riverboat pageant.
He missed the Diamond Jubilee concert at Buckingham Palace and the national service of thanksgiving at St Paul's Cathedral on Tuesday.
In his sermon, the Archbishop of Canterbury said "our prayers and thoughts" were with him.
The Queen was accompanied in her car to the cathedral by a lady-in-waiting, Lady Farnham, and looked emotional at times.
The Prince of Wales sat next to the monarch during the ceremony, and Camilla rode int he Duke's place during the carriage ride back to the palace.
Prince Edward raced off to be with his father before the celebrations were finished.
The Duke will now be hoping to be out of hospital by the time of his 91st birthday on Sunday.
Although the Palace has insisted to the Daily Beast that the Duke's hospitalization is not connected to his exposure to the elements on Sunday, few in the UK believe the two events are unconnected.