The celebrations to mark 60 years on the throne of Britain's Queen Elizabeth ll were tempered by news that the queen's husband, Prince Philip, had been hospitalised with a bladder infection on Monday afternoon.
Palace officials said the prince, who will turn 91 on Saturday, was taken to the King Edward VII Hospital in London from Windsor Castle on Monday as a precaution and will remain under observation for a few days.
Queen Elizabeth walked through St Paul's alone. She was wearing a mint green coat with matching hat.
Despite Philip's illness, many members of the royal family, including Prince Charles, his wife Camilla, Duchess of Cornwall, and Princes William and his wife the Duchess of Cambridge, and Prince Harry attended the thanksgiving service.
The Duchess of Cambridge was wearing a cream lace dress and matching hat.