Method

Chill in the freezer for an hour or so to make the joint easier to slice.
Remove as much fat as possible.
Cut in approx 5mm slices across the grain.
Mix all the marinade ingredients together, add the meat slices and mix well. Store in the fridge for at least a couple of hours/overnight.
Pat dry then place on a rack on a tray and dry in an oven set at 70C for 4 to 5 hours until leathery.
I use a dehydrater for a similar amount of time.