Kate Middleton
Catherine, Duchess of Cambridge, patron of the 1851 Trust, adjusts her helmet as she boards a Land Rover BAR Racing catamaran at Land Rover BAR in PortsmouthChris Jackson/ Getty Images

Kate Middleton clearly knows how to dress like royalty, but this time the Duchess of Cambridge gave a miss to her signature dresses and heels and stepped out in a simple pair of black jeans, a woven jumper and sneakers.

Following a sailing excursion with Olympic champion Sir Ben Ainslie in Portsmouth, London; Middleton dressed down for the third outfit change of her busy day. The 34-year-old Duchess looked classy and comfortable in the casual outfit.

Unlike her usual outings, where she is mostly spotted in heels with well-coiffed hair, the mother-of-two was this time seen strutting in basic black Adidas sneakers with her hair pulled back in a messy bun.

Undoubtedly, the casual look was a refreshing change for the royalty, who spent a rather engaging day at the sailing event. Middleton was supporting the 1851 Trust charity that enables young people to experience sailing, and learn the science and technology related to the sport.

The Duchess of Cambridge arrived at Portsmouth in a themed nautical skirt paired with a white blouse. However, she later changed into comfortable pants and wore a helmet before trying her hand at high-speed sailing.

While returning from the event, Middleton sported the off-duty look with panache, the Duchess seemed to be a pro at steering the boat as well.

Successful Olympic sailor Ainslie was in awe of the Duchess' sailing skills. He said, "I think the Duchess had a great time, it certainly looked that way," adding, "The Duchess was steering the boat for about half of the session and I think the guys were all really impressed with how well she had sailed."

"We had a great sail, it was a blast and she thoroughly enjoyed it," he said.