Prince Harry has been riding a 175mph motorbike after passing his test.
The royal, who is third in line to the throne, received his motorcycle licence after completing an intensive training course.
However, Harry’s interest in the powerful vehicles has sparked concerns among the royal family, who have requested police guards to accompany the prince whenever he rides his bike.
A source told the Daily Telegraph newspaper: “Motorbikes are extremely dangerous and there is only so much Harry’s security team can do to protect him.
“Prince William has given his brother a pep talk on riding a motorbike on the open road. But Harry already appears a better rider and is far more fearless.”
William, 26, gained his motorcycle licence and bought a powerful Honda Super Blackbird two years ago.
Harry’s father Prince Charles is said to be particularly worried about his sons’ safety when they are on their motorbikes.
The source added: “He would far rather the boys stuck to driving cars.”
Meanwhile, it has been claimed William and Harry, 23, are planning a charity motorcycle ride in Africa. The princes are set to travel 1,600 kilometres across South Africa and Lesotho to raise money for people affected by AIDS.
The ride, which will take around a week, was originally set to take place last year. However, plans were scrapped following a security scare. It has been claimed William and Harry’s friends will also join them to make the hazardous off-road journey.
William spent some time in Africa during his gap year, while Harry often travels to the continent with his Zimbabwe-born girlfriend Chelsy Davy.
Harry’s charity, Sentebale, raises money for orphans and those affected by AIDS in Lesotho. Details about the princes’ travel dates, route and accommodation have been kept secret.