However, Kate Middleton‘s at times stern hand reportedly played a huge part in his transformation.

According to a royal expert, the future Duchess of Cambridge didn’t hold back from reprimanding William when he behaved poorly in the early days of their relationship.

WATCH: Prince William and Kate Middleton reveal what they get up to after the kids are in bed

In an article for Vanity Fair in 2008, author Vicky Ward wrote of how Kate felt implored to reign in their partying ways before their royal wedding.

“Interestingly, of the tight-knit royal clique who hit the clubs with increasing regularity, perhaps the most aware of the bad impression they were creating was Middleton,” she stated.

More specifically, the royal observer described an incident during William and Kate’s vacation to Ibiza in 2006:

“On vacation in 2006, Prince William and Guy Pelly, an old friend in the group, often referred to as the ‘court jester,’ were careening around on mopeds in front of a rented house in Ibiza.

“According to a source, Middleton came out of the house and, matron-like, told them to stop.

“She said, ‘Anyone could be watching! Go out the back and stop behaving like this!’

“Like chastened schoolboys, the two did what they were told.

“William may not have liked it, but Middleton’s judgment was almost certainly right.”
According to a royal expert, the future Duchess of Cambridge didn’t hold back from reprimanding Prince William when he behaved poorly. (Credit: Getty)
Shockingly, the writer also revealed that the Duke of Cambridge’s circle made snobbish remarks about his girlfriend, despite her sense of royal decorum.

“There are plenty of snobbish insults from people who, despite Middleton’s obvious attributes, believe that the monarchy needs to stop marrying ‘out’ of its class,” she wrote.

“One member of the young polo-playing set in the county of Gloucestershire – known in the British media as the ‘Glossy Posse’ – noted, ‘Her parents have a tarmac drive, for God’s sake.’”

Ward also noted that William’s sister-in-law, Pippa Middleton was also slammed for desiring to “marry well.”

In his 2011 book William and Catherine biographer Andrew Morton also detailed how Prince William’s future wife felt at the time.

“Kate would have sensed reservations about her in certain quarters,” he wrote.

“While she was seen as a ’pretty and sensible’ girl, there were those in royal and aristocratic circles who believed that the Middletons were too middle-of-the-road for the House of Windsor.”

A Scottish nobleman allegedly told Morton: “It was felt that she wasn’t from the right stock.

“William was expected to find a suitable bride among the aristocracy or European royalty – one of his own kind.

“Kate was treated abominably behind her back by some who should have shown better manners.”

The royal family visited Balmoral this month – over the weekend William and Kate joined Queen Elizabeth, Prince Charles, Camilla Parker-Bowles and several other royal family members at a church service in Aberdeenshire.

Kate and William were also spotted with their children on a budget flight to join the Royal Family on their Scottish retreat and then returned home on a similarly priced airline.

Their budget travel came after Prince Harry and Meghan Markle faced criticism for taking their son Archie on four private jet flights in 11 days earlier this month.

The Duke and Duchess of Sussex – who are expected to announce their second pregnancy soon – are famously eco-friendly and as a result, the royal couple were slammed for their hypocrisy.