Prince William was so handsome when he was still in his teenage years.

A throwback photo when Prince William was still 15 or 16 years old was shared on Instagram. In the snap, the Duke of Cambridge looks dapper in his gray suit. Prince William seems to be in good spirits as he is  all smiles in the picture.

Royal fans couldn’t stop but praise the third-in-line to the throne. One said that Prince William is a “handsome young man.” Another wrote, “So handsome.”

Meanwhile, many also felt that Prince William looks like Princess Diana especially with his smile.

“He definitely has his mom’s smile,” one netizen commented on the photo.

“Like mother,” another follower wrote.

Princess Diana and Prince William were very close. However, the Princess of Wales was not afraid to discipline her son even in public.

According to a newly resurfaced report, there was a time when Princess Diana gave Prince William a smack in public. It happened in school on sports day. The People’s Princess lost her temper after the event had finished. She was ready to leave when the duke suddenly ran away to play with his friends despite the royal mom of two’s disapproval.

“Diana - clearly angry – dashed 100 yards, caught him by the arm and have him a firm smack on the bottom. William burst into tears. He was pushed back into the back of the royal car after a good telling off and driven back to Kensington Palace,” Ashley Walton wrote.

In related news, Princess Diana and Prince William were reportedly not on great terms when Princess Diana died. At the time, the Duke of Cambridge was starting to rebel against his mother, so he was very affected when Princess Diana died in the tragic car accident.

Prince William and Prince Harry also admitted that they regretted their last phone call with Princess Diana. The two boys were in Balmoral when their mom called. However, they were playing with their cousins, so they were in a hurry to end the call not knowing that it would be the last time they would hear Princess Diana’s voice.

Prince William Prince William attends the unveiling of The Victoria Cross Commemorative Paving Stones representing each of Birmingham's 1st World War recepients at the Hall of Memory, Centenary Square on Dec. 7, 2015 in Birmingham, England. Photo: Getty Images/Richard Stonehouse