Andrew Robinson in Nature:
The story of the Indian mathematician Srinivasa Ramanujan (1887–1920) is improbable. Self-taught, he made many seminal discoveries in number theory and power series — most famously concerning the partition of numbers into a sum of smaller integers — that continue to fascinate mathematicians and intrigue physicists studying black holes and quantum gravity. In The Man Who Knew Infinity, director Matthew Brown dramatizes the purest of mathematics for a general audience, and explores the strange personal life of Ramanujan, who died at 32, at the height of his powers, probably from tuberculosis. Based on the compelling biography of the same name by Robert Kanigel (Scribner, 1991), the film took more than ten years to create. It is worth the wait. Ramanujan's career was 'made' by British mathematician G. H. Hardy, a fellow of Trinity College, Cambridge. In 1913, while working as an accounts clerk in what is now Chennai, Ramanujan sent Hardy startling, entirely unproven, theorems out of the blue. “They must be true,” wrote Hardy, “because, if they were not true, no one would have the imagination to invent them.” Hardy lured Ramanujan to Cambridge, even though foreign travel was considered an offence against Hindu caste purity. They collaborated intensively throughout the First World War. Ramanujan had no university degree, but in 1918, Hardy ensured that he was elected a fellow of the Royal Society — the first Indian to receive the honour after it was restricted to scientists — and of Trinity College. They encountered considerable opposition, some of it racially motivated.
Hardy's relationship with Ramanujan holds the film together. Convincing performances by Jeremy Irons as Hardy and Dev Patel as Ramanujan were carefully refined by the film's Japanese–American mathematics adviser, Ken Ono, whose academic career has been dedicated to exploring Ramanujan's theorems. Irons and Patel animate both the consuming passion for mathematics shared by the two, and their astonishing lack of personal intimacy; Hardy, for instance, had only a faint idea of Ramanujan's growing depression, which led to a suicide attempt on the London Underground. Irons, however brilliant, is a generation older than Hardy was in 1914, and Patel is taller and nattier than the more corpulent Ramanujan, who was ill at ease in Western dress.