In my reviews I have observed on more than one occasion that the Brits don't know how to make a bad film. Their challenge is usually in making a great film.

This is a case in point. Technically perfect, with a script so polished it gleams, and acting so sharp that even the secondary roles stay in your head long after the credits roll.

Butterfield's character is a young boy with Autism who, as a result, may or may not be a world class math prodigy. The point of the story however is not whether his character will win a math Olympics but rather if he will ever become a functioning human being.

Butterfield, in a cast of greats, stands out. Has a great career ahead of him, he has mastered the art of delivering dialog with his eyes.

The wonderful Sally Hawkins (Poppy in the unforgettable Happy Go Lucky) does a great job in a difficult role as the mother. Since Butterfield's character as written is constantly ignoring his mother, there is a tendency for the audience to do so as well. Hawkins does not allow this.

It is an excellent film, more a journey than a destination, and therefore not for everyone.

My favourite scene -- the one I will remember for a very long time -- is Butterfield with his (almost) Chinese girlfriend, eating some take-out.

The container is opened and the number of comestibles inside is NOT a prime number. The audience (by that point) has been trained to know this will be a cause of great discomfort for the boy, who likes his meals pre-sorted in prime numbers.

The girl notices his discomfort and he quickly explains the problem to her. With no hesitation she grabs one of the items and wolfs it down happily.

Problem solved! It is a microcosm for the film - start with an impossible boy, add a naturally joyful and spontaneous young woman, and the result is ... serendipity.

Nathan is on the autism scale: though broadly functional, he finds emotional contact difficult, has OCD in certain areas, and so on: however, he is a maths prodigy and is sent to high school early to receive advanced maths tuition from Mr Humphrys, a mildly sardonic teacher in the early stages of multiple sclerosis. Humphrys sets Nathan on course for the British team in the International Maths Olympiad, for which he travels to Taipei and meets Zhang Mei, a non-autistic Chinese girl, also a maths whiz. We see Nathan tentatively exploring difficult areas, and also how other lives in his world change, too.

I had vaguely heard of this film, and was not expecting it to be anything special: it is. Sally Hawkins as Nathan's mum, coping on her own, is phenomenal, and Rafe Spall as Humphrys, blighted with his own problems, is nonetheless very human, both funny and touching. Eddie Marsan impresses me more with every film I see him in: Richard, the administrative head of Team GB is not a sympathetic part, but Marsan gives him some real heart. Jo Yang as Zhang Mei is a delight, and the kids generally are very good, but I must single out Jake Davies as the socially inept Luke Shelton, whose performance is heartbreaking. And this is Asa Butterfield's film. To some extent, giving a "disease of the week" performance is easy if all you seek to do is replicate the physical manifestation of the ailment. Butterfield here goes much, much deeper, and fulfils the early promise of Striped Shirt, Hugo et al.

If I were to be critical, I would say that the ending (which isn't entirely what I expected) could be accused of a little glibness, but that is being finicky. I cried, several times. This is great.

Nathan Ellis (Asa Butterfield) is confused by normal human interactions. His father Michael told him that his superpower is his math abilities but Michael is killed in a car accident when he was a kid. His mother Julie (Sally Hawkins) struggles alone. At school, Nathan is bullied except for irreverent math teacher Martin Humphreys (Rafe Spall). They work towards the International Mathematics Olympiad which Martin was a former participant. Nathan gets accepted and sent to Taipei for math camp led by Richard (Eddie Marsan). He finds other socially awkward math geniuses and Zhang Mei who is often dismissed for being the niece of the Chinese team coach.

The best scene is Sally Hawkins ordering Chinese takeout. This has some good characters, and some good scenes. Asa Butterfield plays autistic well. It would help the story by compressing several of the elements. Going to Taipei adds a little exoticism but it separated Nathan from his two important connections. The story would be more dramatic if he has to deal with Julie and Martin's budding romance. There is simply more possibilities if everybody stays together. The students are great character additions. The movie would work better by concentrating on math camp and staying at home.