Ronald Searle discovered his vocation early, selling his first drawing aged just 15, and becoming an evening-class student before winning a scholarship and studying full-time at the Cambridge School of Art.Photograph: Searle familySick Prisoner of Burma Railway. When the second world war began, Searle was initially assigned relatively easy work as a camouflage artist, but a posting to a troopship later saw him captured and interned by the Japanese in Singapore.Photograph: Chris Beetles Gallery/St James LondonCholera Lines - The Thai-Burma Railway (pen & ink on paper, private collection, courtesy of The Sayle Literary Agency). Searle was later forced with other PoWs to work on the infamous 'death railway' in Siam. He survived close to death during this period, but continued recording sketches of his experience.Photograph: The Bridgeman Art LibraryDebagging Old Flannel Pants. Returned from the war, Searle developed the germ of an idea he had had in the late 20s – and even worked on as a captive – and worked it into what became the hugely successful St Trinian's books.Photograph: Chris Beetles Gallery/St James LondonOK, Make it a Bollinger '29. Photograph: Chris Beetles Gallery/St James LondonIn 1954, a film of The Belles of St Trinian's was a huge hit, and four sequels followed, as well – in 2007 – as an updated version starring the likes of Russell Brand.Photograph: Chris Beetles Gallery/St James LondonSearle became something of a pop culture hero and is seen here visiting an art class at Acton Reynold girl's school near Shrewsbury in 1950.Photograph: Kurt Hutton/Getty ImagesEventually, Searle tired of the St Trinian's bandwagon, and responded to a request from Punch writer Geoffrey Williams to illustrate books based on a wilful schoolboy Molesworth, which became similarly popular. Above is a plate from Welcome Back Molesworth! Photograph: Chris Beetles Gallery/St James LondonSearle was much in demand for other work as an illustrator, painter and even animator. This illustration, advertising rum, was seen on numerous billboards.Photograph: hris Beetles Gallery/St James LondonMonica was Searle's second wife, to whom he remained devoted. She died in July 2011.Photograph: Eamonn McCabe/GuardianWhen Monica was hospitalised with breast cancer in 1969, Searle drew a series of private cartoons of 'Mrs Mole' to cheer her up during arduous therapy. The drawings were only exhibited for the first time last year.Photograph: Courtesy the artist and the Sayle Literary AgencyPartly to escape his celebrity, Searle moved to the south of France, where he was pictured here at home in 2006.Photograph: Eamonn McCabe/Guardian