Thanks Dick, thanks Ken,
A quick search of the Dutton Lainson website shows the offending item in the photos of our winches, and it is described as 'overload protection' in the instruction manual so I think that I'll refit it. Ken, on looking in the box for my spare winch in the garage I notice that there is one of these devices in the box, you are welcome to it if you would like it, just PM me your address.
Phill