One man's extraordinary true-life odyssey - to locate the mother and brother he lost at the age of five - provides the inspiration for Garth Davis' life-affirming drama.

Lion (15)

****

Lion is one of those films where the opening credits are effectively spoilers.

As we see Saroo (Sunny Pawar) struggling to survive in a remote area of India with his mother and older brother, we have already deduced that this cherubic child will, A, be separated from his family, B, be adopted by Nicole Kidman and David Wenham and uprooted to Australia and, C, grow up to be Dev Patel.

The first part of the film, the Indian part of the film, is in the mode of all those classic films about childhood — 400 Blows, Pather Panchali, Kes — films that really see the world through their eyes.

You can't go wrong with a cute kid lost and alone on the streets of a big city.

The second part of the film doesn't quite have the same impact but that's inevitable. Where the first was about movement and danger and visual storytelling, the second is about sitting, security and speaking.

The moment Dev Patel replaces Pawar is inevitably a moment of disappointment – in these long time frame movies, audiences almost always prefer the kid version to the actor that takes the role as an adult.

I should say though that Patel is pretty good in this, playing a man who suddenly comes unstuck inside his own happy and successful life. Here he resembles a young Alfred Molina and his guileless quality comes across as truthful and real.

Lion is the one of those films you expect to be a bland Oscar pleader, so it is a real surprise when there is actually filmmaking on display. Director Garth Davis's storytelling is economical and he has a great eye for where to put the camera.