Vladimir Putin garnered a host of heavyweight detractors over his annexation of Crimea earlier this year, from Barack Obama to Angela Merkel. So far the Russian President has shrugged off international protestations and shouldered sanctions from the US and the EU.
However, the barrel-chested horse rider might be sleeping uneasily in the Kremlin on Wednesday after Prince Charles, currently on a four-day tour of Canada with Camilla, weighed into the debate, comparing the Russian leader's actions to those of Adolf Hitler.
In what amounts to a staggering break from Royal protocol, the Prince made the comparison during an aside to Jewish museum volunteer Marienne Ferguson, who said she had lost relatives in the Holocaust during the Prince's visit to Halifax, Nova Scotia on Tuesday.
The Kremlin has reportedly dismissed the reproach, saying they "couldn't trust" the Daily Mail's report of the encounter, according to The Sun.
According to Ferguson, Charles said: "And now Putin is doing just about the same as Hitler." Asked about the comments, she said: "I must say that I agree with him and am sure a lot of people do. But I was very surprised that he made the comment as I know they (members of the Royal Family) aren't meant to say these things.
"I told the Prince that while my family and I were lucky to get a permit to travel, many members of my relatives had permits but were unable to get out before the war broke out on September 1. They were sent to the concentration camps and died."
To compound the potential fallout from the incident, the Prince is scheduled to meet with Putin for the D-Day commemorations in France on June 6, a meeting that could be thrown into doubt by the Royal remarks.
Sergey Nalobin, the parliamentary counsellor at the Russian Embassy in London, tweeted his displeasure at the remarks. "Members of the royal family do not have the right to make such statements. Parliament is unlikely to be happy," he said.
With regards to the meeting at the memorial, Nalobin said: "As far as I know, a bilateral meeting was not planned. They just will participate in the same memorial ceremonies."
Ukip leader Nigel Farage, who once named the Russian president as a figure he admired and called his handling of the Syria crisis "brilliant", said the Prince should not have weighed in.
"There are times when it might be better for Prince Charles not to get involved in things like this," he said.
Posting on Twitter on Tuesday evening, Labour MP Mike Gapes lambasted the comments. He wrote: "If Prince Charles wants to make controversial statements on national or international issues he should abdicate and stand for election.
"In constitutional monarchy policy and diplomacy should be conducted by parliament and government. Monarchy should be seen and not heard."
If Prince Charles wants to make controversial statements on national or international issues he should abdicate and stand for election— Mike Gapes MP (@MikeGapes) May 20, 2014
But Deputy Prime Minister Nick Clegg told BBC Radio 5 Live that he supported the Prince's "right to have an opinion and express it privately."
"He's a private conversation with a refugee," Royal biographer Robert Harding told BBC Radio 4 Today. "I don't think it should be taken incredibly seriously. The Foreign Office can retreat behind a rather convenient constitutional position, that while he's in Canada, he's the heir to the Canadian throne, so it's over to Canada's foreign minister."
His comments were echoed by Conservative chairman Grant Shapps. "It's not for ministers to comment on what Royals say.Thy can perfeclty well express their opinions as Prince Charles has done," he said.
Although Charles' comments raised eyebrows, he is not the first public figure to make the comparison.
Former US Secretary of State Hillary Clinton made the same parallel in March, when Russia began issuing passports to Ukrainian citizens.
"If this sounds familiar, it's what Hitler did back in the '30s," she said. "All the Germans that were... the ethnic Germans, the Germans by ancestry who were in places like Czechoslovakia and Romania and other places, Hitler kept saying they're not being treated right. I must go and protect my people, and that's what's gotten everybody so nervous."
A spokesman for Clarence House said: "We do not comment on private conversations.
"But we would like to stress that the Prince of Wales would not seek to make a public political statement during a private conversation."