Glashan's cartoons typically included small pen-and-ink figures drawn over a fabulous backdrop often featuring fantastic Gothic or imaginary architecture, surreal landscapes or gloriously impractical ingenious-looking machines.
[1] Glashan's cartoons appeared in Lilliput, Queen, The Spectator, Punch,[1] Private Eye, and various London newspapers, as well as Holiday and the New Yorker.
Glashan's illustrations were also used in advertising material for brands such as ICI, Aalders and Marchant, and Blue Nun.
[2] A series of humorous guidebooks created with Jonathan Routh in the late 1960s allowed extensive expression of Glashan's graffiti-like style, combining small figures (often bearded men) with scrawled text – but, even here, often with elaborate backdrops.
The "Genius" cartoons, which allowed Glashan to use colour and a great expanse of space, ran in the Observer Magazine from 1978 to 1983, whereupon he concentrated on landscape painting.