As the Duke and Duchess of Cambridge said auf wiedersehen in Hamburg, at the end of a five-day tour of Germany and Poland, they were shown a huge Lego model of the liner Queen Mary II.
The 23ft reconstruction was one of two toy boats placed before them at the Hamburg Maritime Museum - the other, a 1:96 scale replica of the Royal Yacht Britannia, the original of which was decommissioned 20 years ago,
Kate was also allowed to play with an orchestra, conducting the Hamburg Symphony at the new Elbphilharmonie concert hall. The musicians followed her baton for a few bars as she attempted the first four notes of Beethoven’s fifth.
Meanwhile, George, who turns four today, made only a brief appearance, alongside Princess Charlotte, clambering aboard two helicopters and trying on a helmet as their pilot father gave them a guided tour of the cockpits, at Hamburg’s sprawling Airbus complex.
“He was excited,” said Antoine van Gent, head of flight testing at Airbus.
“He wanted to sit in the cockpit and then he wanted to sit in the next one. He knew there was a difference.
“Charlotte was also excited. She asked her mother if she could push a button and the Duchess glanced at us and asked if it was okay, and we said yes.”
The prince, whose birthday was marked by the release of an official portrait taken at Kensington Palace, has a busy year ahead of him. In September, he will start school, as one of the youngest pupils in his year at the £17,604 a year private day academy, Thomas’s, in Battersea. The selective establishment says its most important rule is to “be kind”. Its 540 pupils, aged from four to 13, are taught art, ballet and French as well as more prosaic subjects like ICT and physical education.
The Duchess has already said she is not sure George “has any idea what’s going to hit him” as he begins full-time education.
On this week’s tour, he has showed himself to be a somewhat shy royal diplomat. Upon arrival in Warsaw, he needed encouragement from his father to exit the plane, and was seen fidgeting on the red carpet.
As the tour ended, it was George’s younger sister, Princess Charlotte, who misbehaved - falling over and apparently throwing a small tantrum as the royal party competed their final engagement in Germany.
Kate has said she hopes George will keep his “feisty” two year-old sibling in check.
She and William had earlier tried their hand at a cargo ship simulator, which allows visitors to experience what it is like to navigate a vessel into Hamburg harbour.
“Let’s see if I can hit that yacht,” joked William as he took the wheel.
Perhaps overhearing, the volunteer in charge of the simulator, Hans Trey, put Kate in charge.
“He is just the helmsman,” he told her. “You’re the captain.”
Afterwards he said: “They did a wonderful job. He knew exactly how to steer - I didn’t have to tell him.”