LONDON (CNN) -- Queen Elizabeth II's Diamond Jubilee celebrations reached a climax Tuesday, June 5th, but the monarch's elderly husband, Prince Philip, was absent for the service of thanksgiving at St. Paul's Cathedral and carriage procession through London.
The prince, who is 91 this weekend, is recovering at a central London hospital with a bladder infection and is expected to remain under observation for several days. "He is, understandably, disappointed," the queen's press secretary said in a statement Monday.
The service was the formal highlight of four days of celebrations to mark the queen's 60-year reign.
Following a formal lunch, the queen and other members of the royal family returned in procession to Buckingham Palace, through streets lined with members of the armed services and enthusiastic well-wishers.
The queen and the Duke of Edinburgh had been expected to travel together in the 1902 State Landau, the horse-drawn open-top carriage used by the Duke and Duchess of Cambridge following their wedding at Westminster Abbey last year.
But instead, the queen, who waved to those lining the route, was accompanied by Prince Charles and the Duchess of Cornwall. Prince William, the Duchess of Cambridge and Prince Harry followed in a second carriage.
On The Mall, near Buckingham Palace, umbrellas went up as raindrops fell, just as a 60-gun salute began. But unlike on Sunday, when torrential rain soaked the jubilee pageant on the River Thames, the showers held off.
A wave of cheers echoed along the tree-lined road leading to the palace as the sound of horses' hooves signaled the approach of the procession.
The roar of the crowd, which had been waiting hours for a glimpse of the queen, reached a crescendo as the royal family passed by in open-topped carriages.
A flypast over Buckingham Palace by aircraft from the Battle of Britain -- including Spitfires and a Hurricane -- and the Red Arrows display team -- will be the next stage of the celebrations.
The royal family is to appear on the balcony to watch the flypast.
Military marching bands made their way up The Mall after the royals' safe arrival in the palace, followed by thousands of spectators hoping to get close to the palace for a glimpse of the royal family on the balcony.
On her arrival at St. Paul's in the morning, the queen was heralded by a fanfare of trumpets and cheered by thousands of onlookers. Inside, the congregation included Prince Charles and the Duchess of Cornwall, the Duke and Duchess of Cambridge, Prince Harry and UK Prime Minister David Cameron.
During the service, Rowan Williams, the Archbishop of Canterbury, praised the queen's devotion and service -- and also wished Prince Philip well.
"She has made her 'public' happy and all the signs are that she is herself happy, fulfilled and at home in these encounters," Williams said in comments reported by the UK's Press Association. "The same, of course, can manifestly be said of Prince Philip; and our prayers and thoughts are very much with him this morning."
"We are marking six decades of living proof that public service is possible and that it is a place where happiness can be found," Williams added in comments reported by the agency. "To declare a lifelong dedication is to take a huge risk, to embark on a costly venture. But it is also to respond to the promise of a vision that brings joy."
Ahead of the service, thousands of well-wishers crowded against security barriers, flags at the ready, cheering as guests arrived at St. Paul's. During the thanksgiving, those outside, who listened through loudspeakers, joined in as the congregation sang "God Save The Queen."
Later, cheers and applause -- and the pealing of church bells -- greeted the queen and the royal family as they emerged from the cathedral.
Lyn Holgate, from Staffordshire, said she was sorry to have missed a glimpse of the monarch as she passed by, but she had thoroughly enjoyed the celebrations.
"We were lucky enough to go to the picnic garden party yesterday, and we met Princess Beatrice, who said she liked my fascinator," she said. "And on Sunday, the queen waved at us as she was driven past, so there's been a little something every day -- it's been well worth the trip."
Sylvia Corin had an even longer journey, having traveled from her home in Auckland, New Zealand, to be in London for the jubilee.
"I come over for all the big royal occasions," she told CNN. "I was here for the royal wedding last year, and for Charles and Diana's wedding too. Everyone laughs at me, but I think it's worth coming from half a world away."
The grandmother of 14 said she had met several members of the royal family on their trips to New Zealand.
"I took my son to meet the queen when he was 8, to give her a bouquet of flowers, and I've met Prince Charles and Prince William too."
The most notable absentee at St. Paul's, Prince Philip, had been at the queen's side throughout the lengthy jubilee pageant on the Thames on Sunday, as heavy rain lashed the seven-mile flotilla along the river. His illness meant he was not able to attend Monday night's pop concert at Buckingham Palace.
Outside the cathedral, Pip Sweetman, from Portsmouth, southern England, said she had come to show her support for the queen in his absence. "I suppose she's feeling a bit lost today, without Prince Philip," she said.
A small demonstration by an anti-monarchist group was dwarfed by the hordes of royal supporters, but still took a prime spot in front of St. Paul's, where a long-running Occupy protest took place earlier this year.
Graham Smith, CEO of pressure group Republic, admitted the demonstrators were outnumbered but insisted that their presence at the event was important.
"We are here to make sure that the millions of people in the country who oppose the monarchy have their opinions heard," he told CNN. "It is only a token protest, but we're here so the monarchy don't get away with thinking that the whole country is in love with them." But as the queen arrived, the republican shouts of "Make monarchy history!" were drowned out by deafening shouts of "God save the queen!"
Members of the three armed services, military bands and huge crowds of flag-waving well-wishers lined the route as the royals made their way from a reception in the City of London to a formal lunch at Westminster Hall.
The 700 or so guests at the lunch included young people and representatives of different trades, crafts and professions from around the country, with the National Children's Orchestra of Great Britain providing music during the meal. The royals were greeted by a trumpet fanfare as they entered the hall.
The route of the royals' procession from Westminster to Buckingham Palace took in some of the capital's most famous landmarks, including Whitehall, Trafalgar Square and Admiralty Arch.
Squadron Leader Ian Smith, the officer in command of the Battle of Britain Memorial Flight, said the group was honored to be taking part in the jubilee event.
"As a service, the RAF is enormously proud of its heritage, and the opportunity to fly over Buckingham Palace for her majesty with the nation's aviation heritage is something that will remain with us for the rest of our lives," he said.