The name Kitson gave to his research on Cotman was 'Cotmania'. The title stems from a poem written in 1803 by Harriet Cholmeley of Brandsbury Hall, North Yorkshire, in which she praises the young Cotman, her then drawing teacher. All but the last volume are bound in 'Cotman blue' and tooled in gold.
The twelve volumes of 'Cotmania' that Sydney kept from 1926 contain a wide selection of papers regarding John Sell Cotman, including daily journal entries regarding his research, newspaper and magazine cuttings, correspondence, details of sales, transcriptions, sketches, pedigrees, reports, telegrams, photographs and other ephemera. The correspondence comprises material from the descendants and patrons of John Sell Cotman whose collections Sydney discovered, visited, and listed. This is again augmented by Sydney's correspondence with watercolour dealers in Norwich (Boswell), Bradford (Matthews and Brook of whose attributions he was dubious), Birmingham (Thomson), London (P. M. Turner of Sotheby's, Paterson, Meatyard and Palser); as well as with art historians and curators such as Laurence Binyon, Solomon Kaines-Smith, Paul Oppé and James Reeve.
The 'Cotmania' volumes also contain information about Sydney's other professional activities, chiefly his association with the Royal Institute of British Architects (RIBA). Throughout much of his quest for Cotman, Sydney also served as the Honorary Secretary of the RIBA from 1928. With two annual extensions to this role, until 1934 when illness forced him to relinquish such duties in London and Leeds although he continued his task of sorting out the collections deposited in the RIBA library. He was much in demand as an after-dinner speaker, as the Institute's representative at provincial meetings, and he provided useful and experienced support for successive Presidents Sir Banister Fletcher, Sir Raymond Unwin and Sir Gilbert Scott and the permanent Secretary, Sir Ian MacAlister.