After a busy morning of engagements that included a St Patrick's Day parade in Hounslow, West London, the Duke and Duchess of Cambridge flew to Paris to kick off their two-day diplomatic visit.
They headed straight to the the Elysée for bilateral talks with the French President Francois Hollande before attending a reception at the British embassy.
Kate looking suitably chic in a stylish black Alexander McQueen calf-length dress. Her outfit was accessorised with a necklace and earrings with over-sized pearls, Gianvito Rossi heels and a chic bow style leather belt.
The royals were guests of honour at the British embassy reception called "Les Voisins" ("the neighbours") which celebrates cultural ties between the UK and France.
It was followed by a lavish gala dinner at the official residence of the British Ambassador, Edward Llewellyn - Lord Llewellyn of Steep for which Kate made her third wardrobe change of the day.
After Prince William made headlines for his antics during a lads holiday in Verbier, Kate made sure all eyes were on her. She made a showstopping entrance in a sparkling floor-length Jenny Packham gown.
Looking radiant in an ice-silver dress with sheer neckline and elaborate sequin embellishments, the Duchess was the belle of the ball as she mingled with guests.
Among the personalities rubbing shoulders with the royals were some of Paris's more famous residents including French actress Audrey Tatou, Dame Kristin Scott Thomas, who lives in the city, and footballer Robert Pires. The royal couple were also due to meet young French leaders from the worlds of arts, sport, fashion and business as well as young military award winners.
While Prince William maintained a composed demeanour as he addressed the guests, he might have had an unwelcome reminder of his now notorious "dad dancing" to the Pharrell Williams song Happy, as performers Kids United gave the guests a rendition of the Oscar-winning track at the gala dinner. However, bystanders said that the Prince didn't even flinch as they sang.
The royals were treated to a menu of sole crown and Dublin Bay prawns, crayfish, braised leg of Welsh lamb with a seasonal vegetable garnish and roast potatoes with thyme, followed by an iced white and dark chocolate soufflé, butterscotch sauce with a pistachio and almond diamond shortbread.
The royal charm offensive was requested by the Foreign Office in a bid to bolster relations with EU nations in post-Brexit Britain.
Lord Llewellyn, David Cameron's former chief of staff at Downing Street, described the visit as "exciting and special" and revealed that the embassy planned to launch at least one major initiative on the back of it.
"This is the first official visit by the royal couple, the Duke and Duchess of Cambridge, to Paris. This is a country they know well but their first visit is an important and significant moment," he said.
"I have been ambassador for four and half months and been very struck in that time by the deep affection in this country that there is for the Royal Family. I think that is very much evidence today when we see some of the French press coverage.
"This visit underlines the very close ties between Britain and France, countries which are allies, which are friends, but more than that we have the ties of neighbours.
"We will, over the course of this year, celebrate, highlight and underline the ties that go beyond the traditional ties of government, important though they are. They are just one small thread in the rich patchwork at cultural, artistic, sporting and human levels.
"It is also about highlighting the shared challenges we face in this world," he added.
During their time in the French capital the royal couple were due to meet members of the emergency services who dealt with the terrorist attack at the Bataclan theatre in Paris in 2015 in which 130 people were killed, and the terrorist lorry attack in Nice on Bastille Day 2016.
On Saturday (18 March), they are due to visit Les Invalides, the French military hospital, to meet two survivors of the Paris attacks.
The trip also includes tickets to the Six Nations rugby match between France and Wales at the Stade de France, another terrorist target in 2015.