Over time a perception has developed that high-level royals wouldn't and shouldn't wade into political affairs of the day, in part because of how Queen Elizabeth has diligently kept her views to herself.

So when word leaked out that Prince Charles had in a private conversation reportedly likened Russian President Vladimir Putin to Adolf Hitler, the British media were all over it, with one headline even suggesting the whole affair risks "triggering international scandal."

But there is precedent for royals sharing what they think politically, and Charles is far from the first member of his family to cast Russia in a less-than-positive light.

"The Queen's predecessors were more open about their views, and at times Charles seems to follow in that tradition rather than the Queen's approach," says Carolyn Harris, a Toronto-based royal historian and blogger.

The latest controversy emerged in Britain after it was reported the heir to throne had told a volunteer at the Canadian Immigration Museum in Halifax on Monday that, "Putin is doing just about the same as Hitler," relating to Russian annexation of Crimea in Ukraine.

"It has had significant ramifications, because it was uttered by a man who will one day be head of state," BBC royal correspondent Peter Hunt noted on the broadcaster's website today.

Hunt suggests that Charles, "a passionate prince," probably won't be too bothered by the fact he's drawn attention to what Putin is doing.

Others in the halls of the palace and the U.K. government might be more concerned. The Daily Telegraph reported that a senior Russia ambassador is to meet with a Foreign Office official Thursday seeking clarification about whether Charles's remark represented an "official position."

"The comments are regarded as particularly offensive by Moscow as 20 million Russians were killed during the war, including members of Mr. Putin’s family," the Telegraph said.​

Debate has continued for years over just how much Charles, who has controversially waded into everything from organic farming to architecture, can and should say in public and in private.

Letters to ministers

"There have been concerns expressed in the past about how forthright he is with his views and how that will ultimately play into his role as a constitutional monarch," Harris says.

Elizabeth has been on the throne for 62 years, and her way of doing business has become the accepted approach for how monarchs deal with governments, Harris adds. But there have been moments when she let her views be known, too.

Former Canadian prime minister Brian Mulroney has said the Queen was in favour of sanctions against South Africa in the 1980s and the freedom of Nelson Mandela, while Britain's leader at the time, Margaret Thatcher, was not in favour of sanctions, Harris says.

"There are examples of the Queen having made some political views known in the context of her role as the head of the Commonwealth, but generally she's taken her role as an impartial constitutional monarch very seriously," Harris says.

Predecessors, however, weren't as limited in sharing their thoughts on political matters.

"Queen Victoria in her correspondence was quite open about her political views," says Harris. "There were certain prime ministers she liked and certain prime ministers she disliked​."

Some view this as he's learning how the government works and that that makes sense for a future king, and others have viewed this as evidence that he might try to engage in political interference as king. - Carolyn Harris, royal historian

Charles has been known to write letters to government ministers, and there's been much discussion and debate about that, too.

"Some view this as he's learning how the government works and that that makes sense for a future king, and others have viewed this as evidence that he might try to engage in political interference as king," Harris says.

Some correspondence between Charles and government ministers has been the focus of ongoing legal action, with the Guardian newspaper seeking access to 27 letters that were written about 10 years ago.

Of course, Charles's reported comment about Putin, which is similar to a comment former U.S. secretary of state Hillary Clinton reportedly made earlier this year, was out of range of any media microphone.

Clarence House has gone to pains to point that out, noting it doesn't comment on private conversations. Several others, including British Prime Minister David Cameron and a spokesman for the office of Canadian Prime Minister Stephen Harper, have similarly declined to comment on Charles's reported words.

"I understand this was a private conversation, which we were not privy to," said Jason MacDonald, Harper's chief spokesman. "As a result we're not in a position to comment on the remarks.

"That said, we have been clear that the Putin regime's illegal occupation of Ukraine and its persistent military aggression are a return to Soviet-style tactics and cannot be tolerated. We will continue to work with our allies to apply pressure on Russia until they de-escalate."

'Seen and not heard'

British politicians were divided on Charles's reported remark.

"I have never been of this view that if you are a member of the Royal Family somehow you have to enter into some Trappist vow of silence," Deputy Prime Minister Nick Clegg told a BBC morning television show.

But Labour MP Mike Gapes said Charles should end his "freelance foreign policy," the BBC reported.

On Twitter, Gapes said: In constitutional monarchy policy and diplomacy should be conducted by parliament and government. Monarchy should be seen and not heard."

No matter what Charles might say in public or private, the fact that he has a negative view of Russia isn't anything new for his family.

"There's a long royal tradition of distrust of Russia," says Harris, noting it dates back to Queen Victoria's time, coming out of the Crimean War.

King George V, who reigned from 1910 to 1936, was close to his lookalike cousin, Czar Nicholas II, but refused to meet a number of Soviet ambassadors following the revolution there.

Czar Nicholas II, his wife Alexandra, a granddaughter of Queen Victoria, and their family were fatally shot on July 17, 1918. ((Associated Press))

"He claimed to be unwell and [did] not receive the Soviet ambassador because he blamed the Bolshevik regime for the murder of his cousin, Czar Nicholas II and his family in 1918," says Harris. Nicholas's wife Alexandra was a granddaughter of Queen Victoria.

Charles's father, Prince Philip, has also had negative words for Russia. In 1967, when asked if he was interested in visiting there, he said: "I would like to go to Russia very much — although the bastards murdered half my family​."

In the wake of Charles's reported remark about Putin, there has been widespread speculation about the impact it could have internationally. The Daily Telegraph at one point Wednesday topped its website with the headline "Prince Charles 'Hitler' row: 'risks triggering international scandal,' " quoting a report in a Russian newspaper.

Harris doubts it will play out that way.

"I would say there's already an enormous amount of controversy over what's happening in the Crimea and the Ukraine," she says. "It would be extreme to say Charles is triggering an international scandal. It's more that he's made his views known on an ongoing international incident.​"