Research materials collected by Kitson in his acquisition of John Sell Cotman art works and the writing of his biography of Cotman. Kitson's collection of Cotman material was a quest which took him through the many public and private collections of English watercolours to locate and transcribe letters, or copy and often buy drawings.
Advised to live in fresher air on the grounds of ill health, he selected Thornbury House on the edge of Kidlington, near Oxford. 'Queen Anne in front and Mary Anne behind' the house may have been, but it served his purpose well enough, accommodating many fellow Cotmaniacs and Sydney's expanding collection together with his research material and his notes. The visitors book, itself a product of the Arts and Crafts Exhibition at Leeds in 1901, records this flow of Cotmaniacs - Arthur Batchelor of Norwich who introduced him to Mr and Mrs Russell Colman; Brian Belk; Robert Cook, an Australian who took him to Cotman's sites in Normandy; Sir Augustus Daniel, a childhood friend in Scarborough, collector and Director of the National Gallery (1930-1934); Randall Davies, a collector with whom he swapped works; Leonard Duke; Jack Goodison, Keeper of the Fitzwilliam Museum at Cambridge; Sir Henry Hake, Director of the National Portrait Gallery and Sydney's executor; H. lsherwood Kay, Keeper of the National Gallery, transcriber and publisher of part of Cotman's extant correspondence; collectors Agnes and Norman Lupton; Paul Oppé and his family; and Herbert Orfeur, a retired schoolmaster who had inherited a collection of Cotmans.
Friendly rivalry marked the very public mode of collecting in which these scholars, connoisseurs and artists indulged, often competing with each other as well as the dealers who formed an equally close circle. Sydney made a swap with the dealer, Turner, obtaining Cotman's ‘The Falls of the Selune at Mortainin’ in return for two watercolours by Crome of Tintern Abbey. On a visit to Leeds in 1931 Sydney called at the Gallery and identified Robert's 'Normandy sepia' as ‘Vatierville’ of 1818-22. But on 14 November 1933 he referred to having, 'snatched the Normandy [St. Maclou near Port Audemer] church tower from under your nose in Devon'.