Cornwell is probably better known as a mural painter, an American version of Frank Brangwyn. In fact he once rented a studio in London from Brangwyn. His work was seen in the 1939 World's Fair (the General Motors Building), and in Radio City, New York, among other sites. He also undertook masses of advertising work and got particularly involved in imagery for the promotion of War Bonds. His work is technically fascinating. In Watson's book on Forty Illustrators (1946) he reveals that he makes a photostat of his oil study for a piece and projects it on to the canvas (with an epidiascope) to assist in drawing the major lines of the composition.

In 1946 Cornwell admitted to over a thousand illustrations, usually in oil colour. He paid tribute to Howard Pyle who is largely credited with introducing the illustration executed in oil colour - back in the days when a colour illustration in a magazine was a rarity and often framed by the reader.

"An illustrator's task is to focus upon details, action, and effects which are significant in a particular story. Cornwell finds a precise pencil drawing, made on location, ten times more useful than a camera shot."
 
 
 
left "Southampton Docks", April 1947 for the National City Bank of New York .18 x 26cms.

middle War Bond advertisement by Cornwell, July 1944 for Fisher Bodies (General Motors). 21 x 23 cms.

right unknown advertisement for a fruit company, undated.