Artillery Crew With Loading

The British artillery of the Napoleonic Wars was well trained,
efficient and motivated.
Ther officers were very much educated professionals.
They did not, could not, buy their training and schooling was often negated by
the small size of the artillery corps and the fact that promotion was by seniority rather than by merit.

For campaign the gunners wore loose white or grey trousers.
Originally they were worn over the breeches and gaiters. 
Later they were worn in their own right as trousers and the buttoned side fly was abandoned.