The first picture is of a pre production military 6x4 Pioneer fitted with a relatively basic winch possibly made by Scammell, this may not have met military needs, being a bit on the small side.
Which may mean they bought one in (from Wild?) for the 6x6 experiment, but it was too tall for the military version that needed a load bed above it, look where the rear seats are in relation to the drivers one in this pic.
now look at this view of the winch fitted to that 6X6 Pioneer, to me the drive shaft with the brake mechanism and the way it is geared to the drum look very much the same as the Scammell winch.
The text describing this pic states that 'the production military version..........had a vertical axis Wild winch.'
Imagine the drum made larger in diameter and shorter in length, turn it through 90 deg and what have you got? A design collaboration or badge engineering?
Wild were proven winch designers, Scammells may have come up with the idea of a large flattish low profile drum which took some time to get right hence the reported drum failures.
I may of course be completely wrong, feel free to pick this theory to bits and comment