Prince Harry testified in court on Tuesday, in a strongly-worded witness statement that criticised media intrusion into his family's life.
His uncle, Charles Spencer, clearly supports Harry's stance, as he later took to Twitter to share former Labour adviser Alistair Campbell's tweets about the case.
In the posts, all of which the Earl re-tweeted, the politico wrote: "Prince Harry makes a very good point re the damage done to trust in your own circle when stories appear and you have no idea where they come from.
"Some of the biggest fall-outs I had in No 10 arose from suspicions about who was briefing out confidential information. In several of the worst, I now know that the information came not from internal sources but phone hacking or illegal lagging.
Charles' shared the broadcaster's tweets
"Harry may not be able to prove that all of the stories referred to in court came from illegal activity. But that illegal activity was being conducted on a near industrial scale by several papers is beyond doubt.
"That is why I willingly gave evidence. Leveson was the chance to change media culture. For the reasons Harry set out today - the incestuous relationship between press and government - that chance was thwarted.
"I believe in a free press. But I also believe in the rule of law. Both are essential to a healthy democracy. If both press and politicians defend breaches of the rule of law, we do not have a healthy democracy."
What is Prince Harry's court case about?
The case has been brought against Mirror Group Newspapers (MGN) by the Prince and other high-profile figures over alleged unlawful information gathering, including phone hacking.
Prince Harry claims that MGM illegally obtained as many as 140 stories published between 1996 and 2010. Harry is one of four representative claimants whose cases have been selected for trial.
The others are Coronation Street actors Michael Turner and Nikki Sanderson and comedian Paul Whitehouse’s ex-wife Fiona Wightman.
Harry's uncle Charles has had his own battles with the press, with the methods used to obtain Princess Diana's 1995 Panorama interview found "deceitful".
The BBC and journalist Martin Bashir, who conducted the tell-all interview after being introduced to the Princess by her brother, showed Diana forged bank statements that suggested she had been betrayed by her staff.
Lord Dyson, the former master of the rolls and head of civil justice, was appointed to look into the circumstances and his inquiry published in May 2021 concluded that Mr Bashir deployed "deceitful behaviour" to secure the interview, in a "serious breach" of BBC editorial rules.
Reacting to the outcome of the report, Charles took to Twitter to write: "I'd like to thank the TV journalist Andy Webb for his tireless professionalism in bringing the Bashir-Panorama-BBC scandal to light.
If he hadn't have pursued this story for well over a decade, and shared his findings with me last October, today's findings wouldn't have surfaced."
Harry's appearance in court marked the first time in more than 20 years that a member of the royal family has testified since his paternal aunt, Princess Anne, in 2002.
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