Everhard,
To me, the pale-coloured pugarees certainly suggest a colonial unit.
If they have black Sakabula feathers in their slouch hats, they might well be South African Light Horse. Difficult to say though, given that not all the men have the feathers.
Also, the SALH usually have their left brims turned up, whereas these guys have them turned up on their right side.
Rob is better placed to comment on the weaponry, but the piece on the central horse looks like it could be a sporting rifle, and, if so, would again point to an irregular unit.
SALH disembarking from Transport No 37 (Jamaican).
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