Pablo Iglesias has given King Felipe the HBO hit series Game Of Thrones box set as a gift to brush up on his understanding of Spain's "political crisis".
The brazen move by the charismatic leader of the Podemos party, which is topping opinion polls with Iglesias's anti-austerity campaign, happened while the King was meeting the 54 Spanish MEPs at the European Parliament.
"I told him that he is sure to like the series and that it will give him some keys for understanding the political crisis in Spain, " Iglesias told reporters, according to the El Pais newspaper.
It could have been an awkward moment given that Iglesias has previously called for the abolition of the monarchy. He has also requested a formal meeting with the royal and was never given an official response.
But the King accepted the gift with good humour and admitted to Iglesias he had not seen the series.
The 36-year-old is making political history with his party which is surging in popularity and capitalising on discontent over the country's economic problems and high rates of unemployment.
The Podemos party said if it came to power in elections at the end of the year it would hold a referendum on abolishing the monarchy.
"Spaniards should have the right to decide if we have a monarchy or a republic," said Carolina Bescansa, the party's head of political strategy, last December.