The friendship between Britain and France was "forged in sweat and blood" and will not be damaged by the UK leaving the European Union, the Duke of Cambridge has vowed.
The Duke said the historic and cultural ties between the two neighbouring nations will endure, as he mentioned Brexit for the first time on his official visit to France.
He and the Duchess attended a reception at the British Embassy, and laughed as the ambassador joked about France's famous "historically complicated relationship with monarchy".
In a speech opening in hesitant French, the Duke greeted French and British guests at the launch of a new programme celebrating "les voisins" before continuing in English "as to reduce the risk of mangling the language of Molière".
"This deep friendship between the United Kingdom and France, forged in sweat and blood, is one that will endure," he said.
"This partnership will continue despite Britain's recent decision to leave the European Union.
"The depth of our friendship and the breadth of our cooperation will not change."
The sentiments echo remarks he made to Angela Merkel during a visit to Germany last year, and will be seen as a key part of the "soft diplomacy" the Foreign Office hope could assist trade and political relationships.
The Duke added: "So much of our countries’ histories, culture and language are intertwined.
"Those ties of neighbours which run through our history are as powerful today as they have ever been."
The trip has already been noted as the start of a "Brexit tour" of European nations for the Royal family, even as the UK works to extricate itself from the European Union.
All eyes were on the Duke and Duchess as they arrived at the Elysee Palace for the first moments of the two-day trip, greeted by President Francois Hollande on the steps under an array of French and EU flags.
The Duke and Duchess, who wore the same green Catherine Walker coat she had chosen to meet the Irish Guards in London earlier that day, then joined Mr Hollande on gilded chairs inside for photographs followed by a private conservation.
The couple were serenaded with a choral rendition of Pharrell Williams' Get Happy, as they were welcomed to France with a grand black tie dinner at the official residence of the British Ambassador Lord Llewellyn of Steep, David Cameron's former chief of staff at Downing Street.
The Duke congratulated the singers from Kids United, a choir of young French people invited to sing for assembled dignitaries.
The Duchess, wearing a glamorous floor-length Jenny Packham gown and jewellery loaned by the Queen, dined between film star Jean Reno and yachtsman Alex Thomson.
On the menu was sole crown and Dublin Bay prawns, crayfish, braised leg of Welsh lamb with a seasonal vegetable garnish and roast potatoes with thyme, and an iced white and dark chocolate soufflé, butterscotch sauce with a pistachio and almond diamond shortbread for dessert.
The Duke used a short address at the black tie dinner to deliver a message from his grandmother, the Queen.
Recalling her numerous visits to France during her reign, she said: "Although much has changed since my first visit, the ties between our nations have stood the test of time and will, I am sure, continue to prosper."
Lord Llewellyn 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.
He said: "This is a very exciting and special day. 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.
"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.
"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."