Class 40 is a Diesel who once came to the North Western Railway on loan from the Other Railway. In Sodor Adventures, he is known as Bowler, but his status on the railway remains unknown. In Trains, he is named, Wilson.
The Diesel is snobbish and rude, believing that Diesel engines should take over from steam engines.
The Diesel is painted in British Railway's two-tone green livery with a black roof and yellow warning panels.
In Trains, the green is replaced with red.
- Season 2 - Diesel Day and Bluebells Forever
- Season 3 - Percy and the Diesels
- Season 4 - Broken Down Crane
- Season 2 - Diesel of Change