The UK border with the Republic of Ireland is at the centre of the fractious Brexit negotiations and is the key stumbling block between London and Brussels.
His words are applicable to politicians in Westminster and at Stormont.
William has followed his grandmother, The Queen, in calling for a more constructive atmosphere in the national debate around Brexit.
Prince William has spoken at an event in Belfast to celebrate "inspirational young people" from the area.
His language was subtle and the words were chosen carefully, as the Royal Family must operate above politics.
But it’s yet another sign senior Royals do not think politicians are providing the leadership the country needs at a time of great economic and political uncertainty.
He has praised Northern Ireland's first lady of sport, Mary Peters who won a gold medal in 1972, as he urged others to follow her example.
The Duke of Cambridge said: "And as we celebrate those who are leading that change for the next generation, it is also fitting that we recognise somebody else in the room this evening - who helped inspire so many of you in the first place.
"Mary Peters, is not only one of the United Kingdom’s sporting legends, she’s also inspired generation after generation to come together in times of trouble and work for the common good – a lesson I hope many of us can learn from."
Duke and Duchess of Cambridge rowing in Northern Ireland
The UK is currently scheduled to leave the EU on 29 March.
She said: "These approaches are timeless and I commend them to everyone."
Prince William on an assault course in Northern Ireland
The Duke and Duchess of Cambridge have spent part of the day in Fermanagh on the Irish border where they have met children from disadvantaged backgrounds at an outdoor activity centre.
How to keep the UK-Irish border fully open when the UK will be outside the EU has been the biggest stumbling block in the Brexit negotiations.
The Democratic Unionist and many Brexiters in the Conservative party have rejected Theresa May’s plan for the so-called "backstop".
Duke and Duchess of Cambridge playing football at Windsor Park
They fear it could leave Northern Ireland with a different set of customs regulations from the rest of the UK and effectively put a form of trade border between Great Britain and Northern Ireland.
The Assembly at Stormont remains suspended following a dispute between politicians from the two parties in the devolved government, the DUP and Sinn Fein.
As usual with Royal visits to Northern Ireland, William and Kate’s visit was kept secret until the couple landed in Belfast.