The prince has ruffled feathers in China, the US and the UAE in the past, creating headaches for his staff and diplomats alike

Prince Charles's aides can hardly have expected camera crews camped outside Clarence House when they waved him off to Canada on the latest of his official overseas tours.

But as their boss's unguarded remarks to a Jewish museum volunteer in Halifax, Nova Scotia - in which he allegedly compared the Russian president, Vladimir Putin, to Adolf Hitler - reverberated on Wednesday, staff 3,000 miles away at his London residence were busy firefighting.

At such times, and there have been several in the 45 years since his Caernarfon investiture as Prince of Wales, the stock response is: "We do not comment on private conversations."

Given the inflammatory nature of his perceived wading into such a sensitive international issue, however, aides seemed compelled to further clarify: "But we would like to stress that the Prince of Wales would not seek to make a public political statement during a private conversation."

And there's the rub. The prince may not seek to, but he has history when it comes to diplomatic gaffes.

When, on his way back from witnessing the 1997 Hong Kong handover, he described China's ageing leaders "appalling old waxworks", he risked undoing all the benefit imbued by his mother's historic and hugely successful state visit to the People's Republic a decade earlier.

His 3,000-word handwritten dispatch, entitled The Great Chinese Takeaway, was written on the plane and circulated to friends. It exposed his views on the "ridiculous rigmarole" and "awful Soviet-style display" of goose-stepping Chinese soldiers. For good measure, he also bemoaned his uncomfortable club class seat on the British Airways 747 transporting the British contingent back to the UK, and described his indignation at discovering that others, including Edward Heath, Douglas Hurd and Robin Cook were "ensconced in First Class immediately below us".

"Such is the end of Empire," he lamented.

These private views inevitably found their way into the public domain courtesy of a Sunday newspaper in 2006, just days after the Chinese president, Hu Jintao, made a state visit to Britain. Three months later, at the opening of a new Madame Tussauds in Shanghai, the lack of a waxwork Charles from the happy royal group was conspicious.

The Halifax incident highlights the vexed question of just how private the prince's conversations are on official engagements representing the British government.

He was shown around the Museum of Immigration in Halifax by Marienne Ferguson, 78, who told him how she fled to Canada with her family shortly before the Nazis annexed Gdansk in 1939. After the meeting she reportedly said: "The prince said: 'And now Putin is doing just about the same as Hitler.'"

Later she expressed surprise that such a "little remark" had made "such a big uproar". Past experience alone should have taught the prince that such comments rarely remain private, and as future monarch great care must be taken.

The royal correspondents' lot is to trail in the wake of the heir to the throne as he gladhands his way around the planet, and access to those he has just spoken to is usually facilitated. Picking up such stories is the bread-and-butter of royal tour coverage, for which journalists pay hefty prices for airfares and hotels to provide the oxygen of publicity necessary to keep the institution of royalty afloat.

In the United Arab Emirates in 2007, it was McDonald's that attracted the prince's ire, as he told a nutritionist at a diabetes centre that banning the fast food outlets was "key". The company registered its disappointment, adding that other royals had "probably got a more up-to-date picture of us".

In 2010 he attracted criticism for expressing strong opinions on a multimillion-pound plan for Chelsea Barracks in London, telling the prime minister of Qatar, who was chair of the developers, that his heart sank when he saw Lord Rogers' modernist glass and steel design. It was unhelpful timing, with Qatar about to provide the UK with more than 20% of its gas needs, and the Queen due to open a new liquified natural gas terminal in south Wales.

The prince's 2004 visit to Washington was his first to the US in seven years. The long gap, the Guardian was informed by a source at the time, was on the advice of the Foreign Office as he was known to have strong pro-Palestinian views and had been privately critical of US policy in the Middle East conflict.

The Queen has mastered the art of small talk. "Have you come far?' and "what do you do?' are staples. No one should expect this crusader prince to confine himself to inanity, but judgment is still called for.

Next month, he and Putin will both be in France along with Allied leaders including the Queen to commemorate the 70th anniversay of the D-day landings. If the two were due to meet, it seems unlikely now. The timing of his remarks was badly chosen, according to the Russian daily Moskovsy Komsomolets. They risked "triggering an international scandal and complicating the already clouded relations between Great Britain and Russia," it wrote.