The Highland Engines worked on the Highland Railway in Scotland. These engines were painted in a yellow-green livery, and Donald and Douglas nicknamed them Jocks.
When Douglas saw a new engine on the Arlesdale Railway with similar paintwork, it reminded him of his days in Scotland and suggested the name "Jock" for the new engine. The engine was delighted, and the Small Controller happily christened the engine "Jock."
There is only one ex-Highland Railway locomotive in preservation, Jones Goods 4-6-0 no. 103. She was originally in the Glasgow Transport Museum. Following the museum's closure, she was relocated to the Riverside Museum, also in Glasgow.