The artist caused a whole heap of trouble for future, including the Henry difficulties giving the character the wrong wheel arrangement, as well as having TWO tunnels in The Sad Story of Henry as opposed to one.  The illustrations provided by Middleton were replaced by reproductions by C Reginald Dalby instead in 1949, with the originals being discarded and lost to time, consigned primarily to early editions of the book and being very rare to find afterward.  However, the mistakes made by Middleton were picked up by Dalby, and so the problems continued onward...!

William Middleton's illustrations for The Three Railway Engines were soon after replaced by C Reginald Dalby's, which have gone on to become the more recognised and associated illustrations for the book.  Middleton's illustrations were basically very simple, and little reflected any kind of real locomotive, making the characters look very much toy-like as opposed to the desired effect Awdry wished, being the locomotives appearing as real as possible.

The reason for this was that Middleton was an inexperienced illustrator with little idea on scale or drawing people, who had been hired through Edmund Ward's printing connections.  Each of the engines had a flat-disc face, which suspiciously looked like it had been drawn around a coin!

New information has come to light from a reader of the Leicester Mercury about this artist.  The Rev. T. Robin Martin of Birstall shared that William Middleton's 2nd floor studio was over a shop on Halford Street, Leicester. Middleton worked at this location prior to World War II until the 1950s. Believing that no one would be interested is stories about filthy steam engines, "Bill" did not put too much effort into illustrating The Three Railway Engines.

William Middleton

The First & Forgotten Illustrator (1945)