LONDON (AP) - Royal officials say Britain's Prince Philip has missed a gala reception at the last minute because he has fallen ill. Buckingham Palace officials say Philip was "unwell," but added that he will attend a service on Tuesday to mark Queen Elizabeth II's 60 years on the throne. Officials did not elaborate on Philip's health problem. The 91-year-old royal was due to join the queen at a reception at St. James's Palace Monday evening that featured performances by opera group Il Divo. Tuesday's service at Westminster Abbey is expected to draw some 2,000 guests to celebrate the 60th anniversary of the queen's coronation. Philip's health was in the public spotlight last summer when he spent almost a week in the hospital after a recurrence of a bladder infection.