Simon Norton, who has died from a heart condition aged 66, was an Eton-educated maths prodigy considered one of the greatest minds of the 20th century – until the mid-1980s, when he lost his position at Cambridge University and ended up living in squalor in a dingy Cambridge basement packed with bulging plastic bags and piles of bus timetables, living on a diet of tinned mackerel, Bombay mix and brinjal pickle.

In 2011 his story was told by Alexander Masters, his one-time Cambridge tenant, in The Genius in my Basement: The biography of a happy man, a comically affectionate portrait which in the end could not bridge the chasm between the outer and the inner man.

Simon Norton was born on February 25 1952 into a wealthy family of Iraqi Jewish ancestry. He seemed a perfectly normal child until the age of one, when his mother noticed that he was arranging his coloured building bricks into geometric patterns.

At the age of three he had an IQ of 185 (the genius level is reckoned at 140), and by four he was playing with percentages, square numbers, factors and long division. By five he had mastered his 91 times table.

At his prep school, Ashdown House in Sussex, he was useless at every subject other than mathematics, devoting his energy on the sports field to calculating the angles of blades of grass. When he sat the maths paper for a scholarship to Eton he could be heard singing for sheer pleasure at the ease of the questions. He achieved the highest scholarship score in the history of the school.