William and Kate will visit Paris ahead of the Brexit negotiations
Their two-day trip next month will be the first official visit to France for the royal couple since the death of William's mother Princess Diana in a car crash in the city 20 years ago but they will avoid visiting the scene of the tragedy at the Pont de l'Alma tunnel.
The couple, who have both visited France on private trips in the past few years, are being sent by the Foreign Office to Paris to bolster Anglo-French relations ahead of tricky negotiations for Britain's exit from the European Union.
They are expected to meet senior French politicians but sources insisted the trip would not be overtly political and was part of a wider remit to use the Royal Family to maintain close ties with Britain's European neighbours.
The visit on March 17 and 18 comes in the month that Prime Minister Theresa May hopes to be able to trigger Article 50, beginning Brexit negotiations.
A senior royal aide said: "We have a very strong relationship with France and the French people and this visit will celebrate those close ties."
William, who went on a private trip to Paris with Prince Harry to watch England in the Rugby World Cup in 2007, and Kate will attend the Six Nations rugby international between France and Wales and a reception for young French leaders.
We have a very strong relationship with France
Senior royal aide
The royal couple, who have enjoyed several holidays in France, were initially invited to Paris by the Welsh Rugby Union – William has just taken over from the Queen as the WRU's patron – but the Foreign Office then asked Kensington Palace to build an official visit around the match.
In sharp contrast to the glitter of an official royal overseas visit, William, 34, today experienced at first hand the plight of the homeless in London as he launched a new charity helpline.
Opening the Centrepoint Helpline, described as the first advice centre for young people who are homeless or at risk of being homeless, he listened in as a young rough sleeper called for help.
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The two-day trip will be their first official trip to France
William was so struck by the teenager¹s situation that he asked to be kept up to date with what happened to him.
The new helpline, which went live today, aims to help young people with advice and support on housing, as well as related issues including mental health, relationships, money and work.
William, who is patron of Centrepoint, listened in as call worker Carys Lewis took a call from a teenager who had been robbed twice while sleeping rough.
The teenager had been thrown out of home after an argument with his parents, and had been sleeping outside and in late-night cafes.
The couple are being sent by the Foreign Office to bolster Anglo-French relations
The second in line to the throne, who was clearly struck as Ms Lewis went through the options for the teenager, including going to a night shelter as a first step, told her afterwards: "Will you let me know how he gets on? I would like to know."
According to a YouGov poll commissioned by Centrepoint, 17 per cent of young people have at some point felt they had nowhere safe to call home.
The Royal Family to maintain close ties with Britain's European neighbours
As a result of this, 65 per cent have sofa-surfed, 35 per cent have stayed where they were living even though it wasn't safe, and 31 per cent have slept in an insecure place, for example, on the streets, in a car or tent, or squatted.
Seyi Obakin, the chief executive of Centrepoint, said: "Today is an important day for all young people, not just those that are homeless. Homelessness is not that far away. It can happen to anyone. What the helpline is going to do is give them a lifeline."