Unshakable, witty and deeply felt, the film will be paying emotional dividends for a long, long time.

The film never slows down or bores, plunging from one harrowing sequence to the next.

It's funny, it's tense, it features two great performances from two actors and the director expertly creates a web of odd tension where you actually don't know what is happening for the majority of the run time.

It's the kind of movie you'll want to see a second time with someone who hasn't seen it yet, to remember what it was like to watch it for the first time.