A loss of focus turns this small English feature from an excellent film into a routine and mediocre one about half-way through, but its opening reels have touches of understated genius about them and it is full of undeniably moving moments.
It's the dramatic debut for director Morgan, an acclaimed maker of TV documentaries, who based it on his 2007 Spellbound-style doco Beautiful Young Minds, which followed the British team as it prepared for and took part in the International Mathematical Olympiad.
The beautiful young mind he follows here is that of Nathan Ellis (Baker-Close and later Butterfield), an autistic youngster who lives with his widowed mum Julie (Hawkins) in suburban Yorkshire.
Nathan's preternatural talent for maths comes to the attention of his teachers and he starts taking private lessons from a teacher called Humphreys (Spall), whose encroaching multiple sclerosis lends him just the right blend of sardonic worldliness and existential angst.
Their aim is to get Nathan into the national Maths Olympic team and about the only thing the film doesn't do wrong in its second hour is that it avoids the hackneyed triumphal ending.
