Prince George - who has undoubtedly tried to be very good all year - has asked Santa for a police car for Christmas, promising that he has been "nice" all year.
Rather than putting the letter up the chimney, or even posting it to Santa, the Duke of Cambridge personally delivered Prince George's handwritten note to Father Christmas on the final day of his two-day trip to Finland.
Presumably the four-year-old was requesting a toy car for Christmas as he will not be old enough to sit his driving test for 13-and-a-half years.
When the schoolboy's father met jolly old Saint Nick during a trip to a Christmas market in the capital, Helsinki, he pulled the letter from his suit jacket pocket, telling Santa: "I've seen you and I had to give you this letter."
Laughing, Prince William added: "He hasn't written down many requests, so I think one request is probably ok."
Santa scrutinised the form, which had been filled in by the future king and began with the printed words: "Dear Father Christmas this year I have been naughty/nice."
Prince George had circled "nice", written in large letters "police car", as well as writing his name at the bottom.
Prince William insisted to Father Christmas that George had "been a nice boy, a nice boy", pointing to the word on the letter.
Santa, who traditionally is from Finland, nodded his head in agreement and duke smiled again.
After passing Prince George's request to Father Christmas, the duke asked him if he had "come all the way from Lapland", remarking it must be a "busy time" of the year for him.
Prior to meeting Father Christmas, Prince William met hundreds of well-wishers who had braved the freezing cold to meet him in a nearby park.
The duke spent time shaking hands, chatting to people and joking with the crowds as he slowly made his way down the line of people.
The 35-year-old also met members of Finland's air force at Helsinki airport where military aircraft were on display, and attended a tech festival in the city.
The second-in-line to the throne also visited a school to learn about the ways in which the Finnish education system is attempting to put student welfare and mental well being at the top of its agenda.