Prince William, 34, who is colonel of the Irish Guards, and Princess Kate, 35, visited the 1st Battalion Irish Guards at their base and later joined officers and their families for a pint of Guinness. The couple received a "hip hip hooray" toast from officers at the barracks.
William and Kate, who wore an evergreen Catherine Walker coat and matching heels, traditionally present shamrocks to the regiment before they march in a parade. They were joined by the officers' honorary mascot, an Irish wolfhound.
The event was William's first official engagement since a weekend-long break in Switzerland where he was caught "dad dancing" at a nightclub and criticized for missing an important Commonwealth Day service at Westminster Abbey attended by other members of the royal family.
Following today's lunch with the Irish Guards, William and Kate boarded a charter plane for a two-day official visit to Paris. The couple will serve as unofficial ambassadors in Paris, utilizing soft diplomacy as the U.K. negotiates its exit from the European Union.
The royal family has scheduled a series of visits to European countries in the months ahead -- including William's and Kate's July visit to Germany and Poland -- to remind Great Britain's European neighbors that they are still allies and partners after last summer's Brexit vote.
William and Kate are scheduled to attend a reception and black-tie dinner tonight at the British ambassador's residence, where the couple is reportedly staying during their visit. The residence, built in the 18th century, is one of the best known buildings in Paris and is located close to Elysee Palace, the home of France's president.
On Saturday, William and Kate will visit Les Invalides, a Paris landmark known for its golden dome that includes the Tomb of Napoleon. They will also meet with survivors and first responders from the July 2016 terror attack in Nice, France, and the November 2015 terror attack at the Bataclan.
William famously showed his solidarity with the French people just days after the Bataclan attack, which also targeted a soccer game at Stade de France. William attended the England versus France soccer match at London's Wembley Stadium and sang the French national anthem in support.
In another symbolic show of support, William and Kate will travel Saturday to Stade de France to watch France take on Wales in the Six Nations rugby match. William is royal patron of the Welsh Rugby Union, a position he took over from his grandmother, Queen Elizabeth, in December 2016.