The Duke of Cambridge has repeated his belief that Britain and Germany will remain "the firmest of friends" despite the UK's decision to leave the European Union.
William, echoing comments he made last year during a trip to Germany, told guests at a Berlin garden party the relationship between the two countries "really matters".
The Duke's three-day tour of Germany, with Kate and their children Prince George and Princess Charlotte, is another in a series of visits by the monarchy to Europe this year that have been dubbed Brexit diplomacy trips.
The young prince and princess made an appearance earlier when the Duke and Duchess flew from Poland to Berlin and they were seen boarding and leaving the couple's private charter jet.
Charlotte stole the show by scampering up the plane's steps in Warsaw and receiving her first official bouquet in Berlin.
Speaking at a garden party celebrating the Queen's birthday, William told the guests: "The United Kingdom and Germany proudly share the same values as open and democratic societies, and the same determination to champion those values and to defend them - not least through our very close defence and security partnerships.
"Today, we share a fundamental interest in the peace and prosperity of the continent of Europe to which we both belong.
"This relationship between the United Kingdom and Germany really matters. It is the product of many years of working closely together.
"It will continue despite Britain's recent decision to leave the European Union. I am confident we shall remain the firmest of friends."
A few months after last year's Brexit referendum, William gave a speech at a gala in Dusseldorf alongside Chancellor Angela Merkel and stated the "depth'' of Britain's friendship with Germany would not change after the decision to leave the EU.
At the garden party event Kate wowed guests wearing a stunning off-the-shoulder red Alexander McQueen dress with cream open-toe heels.
Britain's ambassador to Germany Sir Sebastian Wood hosted the evening but he was left a little red faced before a toast to the Queen when he spotted Kate and William were empty handed.
He told the crowd: "Oh dear. We have no glasses. This is where we do what the British say and, 'Keep calm and carry on.'"
As the party waited and no drink appeared, he said: "No I'm sorry. I won't carry on. There are hundreds of glasses here, can we please have one?"
Kate and William, who were standing just behind the ambassador, laughed before they were finally handed a flute each to join the toast.
The couple later mingled with guests who packed the lush green grounds surrounding the ambassador's sprawling home in Berlin sipping Pimms and champagne.
Mr Wood thanked William and his family for visiting and added: "It is the sign of a long and happy relationship between you and your family and this wonderful country."
The Duke also read a message from the Queen who reiterated the close ties between the UK and Germany.
She said: "We have fond memories of our five state visits to Germany, from our first in 1965 to our most recent in 2015. Over the course of those 50 years, British-German relations have thrived, allowing us to face the challenges and embrace the opportunities of the 21st century together."