"We'll put these in his pockets," said William. "Then we'll know where he is in the house!"
Prince William said the Christmas bells would help him keep track of Prince George
The Duke of Cambridge was attending the tenth anniversary gala at the Imperial War Museum in his role as Royal Patron of SkillForce.
Dressed smartly in a black suit and bow tie, the 32-year-old Prince spoke to those who have recently taken part in the SkillForce Junior Prince's Award, which he launched last year.
Youngsters from three primary schools in Watford gathered to proudly show the Duke their project, which was focused on the theme of Remembrance.
Prince William is the Royal Patron of SkillForce
The artwork showed a man adorned with poppies, and ten-year-old Thomas Brooker explained to William that "each of the poppies represent a soldier who died."
Anmer Hameed and Laura Stafford, both aged nine, also spoke to the Duke about some of the sports they had been doing as part of their award, prompting him to joke, "You'll have to teach me dodgeball."
SkillForce uses the skills of ex-Forces personnel to inspire young people aged nine to 19 to succeed. Among its many aims, the organisation works to reduce truancy and exclusion in schools, improve attitudes and behaviour of young people and help students go on to positive destinations such as work or training.