Although A Royal Night Out opens with somber real-life images of Londoners taking to the streets as Germany’s World War II surrender is announced, the rest of the movie is almost entirely frivolous, a heavily fictionalized story about the adventures of teenage princesses Elizabeth (Sarah Gadon) and Margaret (Bel Powley) as they cavort around the city on the night of V-E Day. The prim Elizabeth engages in flirty banter with a working-class airman (Jack Reynor), while the more free-spirited Margaret gets whisked off to shady nightclubs, as they both conceal their royal identities. Gadon and Powley are charming (and Powley gets unfairly sidelined for Elizabeth’s predictable romantic storyline), but the movie can’t quite settle on a tone, landing somewhere between The King’s Speech and The Princess Diaries. The silly fun and the rudimentary personal reflection come off as equally superficial, and end up equally forgettable.

A ROYAL NIGHT OUT Sarah Gadon, Bel Powley, Jack Reynor. Directed by Julian Jarrold. Rated PG-13. Opens Friday.