Kate Middleton, Prince William Salute Queen Elizabeth II at Service of Thanksgiving

Prince Charles, Prince of Wales, Prince William, Duke of Cambridge, Camilla, Duchess of Cornwall, Catherine, Duchess of Cambridge and Prince Harry leave a Service Of Thanksgiving at St Paul's Cathedral on June 5, 2012 in London, England. Credit: Matt Cardy/Getty Images

All hail Queen Elizabeth II!

Her Majesty was surrounded by her family, friends and loyal subjects at Tuesday's service of thanksgiving at St. Paul's Cathedral in London.

Her husband, Prince Philip, Duke of Edinburgh, 90, was not in attendance, as he was recently hospitalized "as a precautionary measure after developing a bladder infection," a Buckingham Palace spokesperson recently told Us Weekly. As a result, Queen Elizabeth II traveled with her lady-in-waiting, Diana Marion, Lady Farnham.

Kate Middleton, 30, and her husband, Prince William, 29, arrived at the cathedral several minutes before Queen Elizabeth II. They joined Prince Charles, 63, Camilla Parker-Bowles, Duchess of Cornwall, 64, Prince Harry, 27, Princess Eugenie, 22, and Princess Beatrice, 23.

"Kate spoke with Camilla at the West Door before the service started," an observer tells Us. "They were smiling and chatting."

(Middleton wore a pale pink Alexander McQueen dress, LK Bennett heels and a Jane Taylor hat; Bowles paired a Bruce Oldfield coat and dress with a Phillip Treacy hat.)

Once inside, Middleton sat in between William and Harry. "Harry discreetly ate a mint during the service," an observer tells Us.

During his sermon, the Archbishop of Canterbury, Dr. Rowan Williams, said: "I don't think it's at all fanciful to say that, in all her public engagements, our Queen has shown a quality of joy in the happiness of others; she has responded with just the generosity St Paul speaks of in showing honor to countless local communities and individuals of every background and class and race."

"She has made her public happy and all the signs are that she is herself happy, fulfilled and at home in these encounters. The same, of course, can manifestly be said of Prince Philip; and our prayers and thoughts are very much with him this morning," Williams, 61, continued. "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."

Williams continued to praise the monarch, saying: "We are marking today the anniversary of one historic and very public act of dedication -- a dedication that has endured faithfully, calmly and generously through most of the adult lives of most of us here. We are marking six decades of living proof that public service is possible and that it is a place where happiness can be found."

On Monday, musicians including Elton John, Kylie Minogue, Paul McCartney, Tom Jones, Cheryl Cole, Stevie Wonder and Jessie J paid tribute to Queen Elizabeth II during the Diamond Jubilee Concert. "Kate sang 'la la la' along to Kylie's 'Can't Get You Out Of My Head,'" an observer tells Us of Middleton. "It looked like she wanted to get up and dance, but stayed in her seat."

The night ended with a massive fireworks display and a speech from Queen Elizabeth II's son, Charles. "Your Majesty, I'm sure you want me to thank on your behalf all the wonderful people who made tonight possible. The performers, the comedians who made those jolly good jokes. . . and, above all, the technicians, all 600 of them," he said. "The only sad thing about this evening is that my father couldn't be here. . . but ladies and gentlemen, if we shout loud enough he might just hear us in hospital."