Wigfull most often signed his illustrations "W.E. Wigfull". The attribution of the W in a box monogram was secured via an illustration for an article by 'Sabretache' called "Pictures in the Fire" which was published in "The Tatler" for 1917 October 3, Page 6.
Wigfull also used the "W." in a box monogram for some of his illustrations in the 1914 edition of Westerman's "The Log of a Snob".