On Friday, the Duke and Duchess of Cambridge went public with their concerns over the paparazzi's behaviour towards their son, Prince George. The royal couple expressed their concern over the "increasingly extreme lengths" that paparazzi will go to in order to capture covert images of Prince George, which can fetch a lot of money for the photographer.

In a frank open letter posted on Prince William's official website, Kensington Palace's communications secretary, Jason Knauf, revealed various incidents of the paparazzi hounding the Cambridges during their private time with their two-year-old son, Prince George.

"It is clear that while paparazzi are always keen to capture images of any senior member of the Royal Family, Prince George is currently their number-one target," Knauf's letter reads.

"We have made the decision to discuss these issues now as the incidents are becoming more frequent and the tactics more alarming. A line has been crossed and any further escalation in tactics would represent a very real security risk," he wrote. 

He revealed that the police had discovered a paparazzi photographer camped out in a vehicle with darkened windows beside a public children's playground, in an attempt to score images of Prince George. "The worry is that it will not always be possible to quickly distinguish between someone taking photos and someone intending to do more immediate harm," Knauf wrote.

He also warned the part that the public are playing, albeit unknowingly: "We are aware that many people who read and enjoy the publications that fuel the market for unauthorised photos of children do not know about the unacceptable circumstances behind what are often lovely images," he wrote.

"The use of these photos is usually dressed up with fun, positive language about the 'cute,' 'adorable' photos and happy write-ups about the family."

He added that whilst the Cambridges are happy to share images of their children (such as the official ones taken by Mario Testino) "they know that every parent would object to anyone – particularly strangers – taking photos of their children without their permission."

Saying that the royal couple "feel strongly that both Prince George and Princess Charlotte should not grow up exclusively behind palace gates and in walled gardens. They want both children to be free to play in public and semi-public spaces with other children, and without being photographed."

Knauf said the palace hoped that by bringing these issues to the public's attention it "will help all publishers of unauthorised photos of children to understand the power they hold to starve this disturbing [and lucrative] activity."