It's a sometimes hard-hitting, always heartfelt film - and star Bel Powley is an actor with an umami-style knack for adding depth to any film she's in.

It is relentlessly bleak, but within that tonal bleakness there is some really striking imagery.

Filmmakers never seem to run out of footnotes to history during World War II. This one is better served in the pages of a novel. It doesn't work on film.

Without those redemptive highs or soul-destroying lows to stir the emotions, the overall effect can be a bit numbing, making this a rather forgettable tribute to the countless victims of Soviet oppression.