They had steam engines to begin with and then a diesel.
The locos belonged to the factory and shunted the sidings which connected the industrial network with British Railways.
We've seen only one picture of such a loco - in the North Lincolnshire Museum Image Archive.
Perhaps others have survived in the Brigg area?
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There used to be a very small British Railways signal box called Brigg Siding that was used to control trains of wagons entering and leaving the factory.
The factory was a major employer in the Brigg area from the late 1920s until closure in the mid-1990s.
There's an ex-employees' reunion every autumn.