“A Royal Affair,” from Denmark, tells an amazing real-life story from Danish history that has everything going for it - sex, love, terror, politics, violence. A beautiful young royal from England is brought to Denmark to marry King Christian VII, sight unseen. And then she meets him, and he’s borderline insane, lashing out at people without warning and masturbating around the clock. What a guy.

Mikkel Boe Folsgaard won the best actor prize at the Berlin Film Festival for his performance as the king, a terrifying weakling who, yet, has a soul. When a German doctor, Struensee (Mads Mikkelsen), is brought in as the king’s personal physician, Christian gets a little better. He has a friend. And gradually, he starts taking Struensee’s advice on how to run the country - along more populist and liberal lines.

As played by Mikkelsen, Struensee is just so much more of a man than the king that everyone notices it, including the queen, who is young and love-starved. And so we have this pressure cooker situation: As long as the king listens to Struensee, Denmark will get better. But if Struensee and the queen consummate their understandable attraction - they’re the best looking and most sane people in the country - they risk everything.

If Christian VII is the film’s flashiest character and the queen its most sympathetic, Struensee is the most fascinating, a man of relaxed demeanor and fierce ambition, unusual perception and tin-eared cluelessness. Mikkelsen has the aura of a man who can never make a mistake, until you realize that he can.

“A Royal Affair” is an engaging and entertaining film, one that might have been great, if only the history were different. Danish history collaborates with the filmmakers for about three-quarters of the running time, but so long as the film is committed to presenting a version of the truth - as it should be in a movie like this - the last quarter was bound to disappoint. “A Royal Affair” is magnificent when it plays just like a movie, and less so when it becomes like real life.