Princess Maxima of the Netherlands led the contingent of European royals who watched Pope Francis's inaugural mass in Rome.
The Argentinean-born royal, who looked radiant as she chatted with Letizia of Spain, watched with particular interest as countryman Jorge Mario Bergoglio gave his first sermon in St. Peter's Square.
Vatican protocol dictates that papal audiences wear black, and Maxima and her fellow female royals looked striking in demure outfits and distinctive lace veils, known as mantillas.
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Holland's future Queen was clearly delighted to watch an Argentinean secure his place as the 266th head of the Roman Catholic Church.
The princess and husband Willem-Alexander took their places next to Letizia and Felipe of Spain during the open air mass.
Other European royal houses were represented by Prince Albert and Princess Charlene of Monaco, Grand Duke Henri and Grand Duchess Maria Teresa of Luxembourg, Prince Felix of Luxembourg and King Albert II and Queen Paola of Belgium.
The Duke and Duchess of Gloucester represented the UK at the celebration, which marked the beginning of the Petrine Ministry of the newly-elected pope. Prime Minister David Cameron didn't attend.
All of the royals took their place alongside some 31 heads of state who had travelled to mark the inauguration of the religious leader, whose emphasis on social issues has earned him the name "The People's Pope".
The excitement was tangible in St. Peter's Square, where an expectant audience gathered in the bright spring sunshine to witness an important moment in history.
Earlier in the morning, Pope Francis brought the Vatican City to a standstill as he arrived in an open-topped vehicle. The bells of Saint Peter's Basilica pealed out around the bustling square, competing with cries of "Viva il Papa" – "Long live the Pope."
The pontiff delighted crowds when he repeatedly stopped his journey to interact with followers. He ordered drivers to stop his car and climbed down to kiss a disabled man and a tiny baby who caught his attention.
Shortly after 9:30am, the Pope rose from the presidential chair and delivered a softly spoken Latin prayer which officially installed him as head of the Catholic Church.
Francis received a customised ring and the pallium – a wool strip representing the Pope's role as a shepherd – as symbols of his new powers.