Prince Harry and his brother William love to "bomb" around fields on their motorbikes to "shake the cobwebs out", he has revealed.
The release of a third picture by photographer Mario Testino to mark the prince's 21st birthday, has led to further insight into the royal's life.
The colour image sees a muddied third-in-line to the throne straddled across a motorbike.
The prince said the photo was to capture something of the real Harry.
Three images of the prince - all by Testino, who also photographed Princess Diana - have been released, along with press interviews, to mark his birthday on Thursday.
The latest was taken at Prince Charles's organic Home Farm in Gloucestershire.
Harry is seen wearing red, white and black biker gloves, a grey T-shirt and wristbands, and with strategically-placed dirt on his forehead and chin - put there by one of Testino's assistants.
"We had this idea - instead of making sort of fake photos - for me to be who I am," the prince said.
"Well, to a certain extent, rather than turn up in scruffy clothes.
"He asked me to go on my motorbike. This one was actually William's one. Mine's a Yamaha 125.
"It's something that we bomb around the fields on - it's a way of shaking the cobwebs out."
He said action shots were out of the question because of a lack of helmet.
"I didn't ride it today for legal reasons," he said.
Older brother William, 23, owns a Yamaha 600 trials bike, as well as a Triumph Daytona 600, which has a top speed of 165mph and is the nearest thing to a racing bike allowed off the track.
Celebrations for Harry's 21st were reportedly subdued as he is currently training as an Army officer at Sandhurst military academy.
In interviews released on that day, the prince said he loved his stepmother, the Duchess of Cornwall, "to bits".
He also apologised for a Nazi fancy-dress costume he wore to a party, paid tribute to his girlfriend Chelsy Davy and maintained he was not going to be "some person in the Royal Family who just finds a lame excuse to go abroad".