To Burger King, it probably seemed like an innocent game. To promote the launch of the first Belgian Burger King, the chain (whose ads that hit bull’s-eyes have been winning it acclaim) has launched an ad and online game on its website, which asks, Two Kings. One crown. Who will rule? Vote now … Visitors get to choose their monarch – King Philippe or the Burger King.

Choose Burger King and the site presents you with an image of a voting booth so you can share your choice on social media. Choose King Philippe and the site keeps badgering you with various permutations of the question, “Are you sure?”, to try to get you to change your mind.

“Are you sure you want to pick King Philippe? He won’t be making you fries.”

It is impossible to choose King Philippe.

This angered the Belgian Palace. “We told them that we were not happy with them using an image of the king in their campaign,” Palace spokesman, Pierre-Emmanuel De Bauw, told Reuters, which reported the gaffe. The monarchy would not have authorised any images of King Philippe for commerce, De Bauw added in a statement to the BBC. A cartoon image of Philippe appears in the ad.

The ad is particularly sensitive because it appears to mirror an event in 1950, when Belgium held a referendum that resulted in Philippe’s grandfather, Leopold 111, being forced to abdicate in favour of his son, Baudoin, because Belgium had surrendered to Germany in 1940 after declining to become allies with Britain and France.