Definition of "unpiloted"

The trouble has been mainly due to the preceding 6.40 p.m. Sheffield express, which since being demoted from an "XL Limit" to a "Special Limit" schedule had presented unpiloted Class "6" 4-6-0s with loads at times up to 12 bogies. [In railway parlance "unpiloted" means the train had no pilot engine double-heading it.]

1959 October, Cecil J. Allen, “Locomotive Running Past and Present”, in Trains Illustrated, page 479