[3] Between the two world wars Henderson travelled extensively in Africa and South America and would later include images of the flora and fauna he saw on these trips in his book illustrations.

He illustrated books by W. H. Hudson and E. R. Eddison, including The Worm Ouroboros, and, with Norman Wilkinson, an edition of Geoffrey Chaucer's translation of The Romaunt of the Rose.

[4] He also exhibited his work, at the Royal Academy[10] and a solo show of paintings of Cyprus at the Beaux Arts Gallery at Bruton Place in London.

Although the painting An Improvised Test of an Under-carriage provoked fury in the Air Ministry and contributed to Henderson's six-month contract not being extended, it was among the artworks shown at the first WAAC Britain at War exhibition at the Museum of Modern Art in New York in May 1941.

[20] After an interval of great heart searching he moved to London, having sold their Scottish home and his complete collection of pictures and books.

[20] During the last twenty years of his life, Henderson engraved over sixty illustrations for a book on Assyrian, Egyptian and Greek mythology which he titled Creatures and Personages, but which remained unpublished at the time of his death.

[16] All entries are illustrated by Keith Henderson, the first five with colour plates, the remainder with pen-and-ink drawings or engravings in black-and-white, unless otherwise stated.