Prince George is "very envious" of his father Duke of Cambridge for driving a digger.
The 35-year-old royal was getting evil glares from his four-year-old son after he recently visited the Defence National Rehabilitation Centre, near Loughborough, where he got to drive a tractor.
Speaking at a pre-dinner speech at the City Veterans' Network fundraising gala, which was held at the Imperial War Museum last week and has been reported on the Telegraph Online, Prince William - who also has two-year-old daughter Princess Charlotte with his wife Duchess Catherine - said: "I have been repeatedly impressed by both the speed and ambitious scale of this endeavour.
"I was present at the end of 2014 when the first building was demolished to make easy for the new construction.
"George was very envious as I got to drive a digger."
And William believes the site will have the "very best rehabilitation facilities" in comparison to anywhere in the world.
He said: "It will give the brave men and women of our armed forces access to the very best rehabilitation facilities on offer, anywhere in the world. You will all agree with me that they deserve nothing less."
And William's oldest son has a fondness of mechanical equipment and planes, and he knows everything about "all the parts".
Speaking about George's interests, Pauline Hallett of Ogwen Mountain Rescue previously said: "William used to fly us around when he lived and worked up here and I was telling him about the new helicopters.
"Catherine then said how much George loved them. He knows all the different colours and asks her about all the parts.
"She laughed and said she tells George to ask daddy as she has no idea."