(CNN) Royal visits overseas always attract a great deal of scrutiny, but none in recent memory has been quite as politically sensitive and potentially inflammatory towards the UK's closest ally than this one.

When Prince Charles and his wife, Camilla, set foot in Havana Sunday, they'll be making history by embarking on the first ever official visit to Cuba by members of the British royal family. But they're doing so at a time when much of the western world is denouncing Cuba's role in the unfolding political and humanitarian crisis in its close socialist partner, Venezuela.

It's a trip that would have seemed impossible only a handful of years ago, before former US President Barack Obama and former Cuban President Raul Castro thawed more than half a century of tense relations between the North American neighbors and their allies. But since that 2016 breakthrough, the world is a very different place.

President Donald Trump has reversed many of the Obama-era policies toward Cuba, reinstating travel and trade restrictions. His sharp rhetoric has only become more aggressive since the presidential crisis unfolded in Venezuela. The role of Cuban military and intelligence advisers serving the disputed regime of President Nicolas Maduro is one of the main concerns of the US administration and its allies.

"For decades, the socialist dictatorships of Cuba and Venezuela have propped each other up in a very corrupt bargain," Trump said in February, adding: "Maduro is not a Venezuelan patriot; he is a Cuban puppet."

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