I have 1996 ford iveco daily 59-12 ex mobility minibus ?

The spare wheel is underslung on the near side and there is a square hole in the body corrisponding with a cone shaped winch head about 300mm inside the van
the winch looks to have a 16mm approx square socket within and although I can insert a chisel into the socket and turn it both ways it doesnt release or tighten the wire support to the spare.
Anyone know what the lowering tool looks like and where I might get one.

thanks