Soak the wood chips for the smoker in water before use.
Place the redcurrants and sugar into a saucepan over a medium heat and cook for 2 – 3 minutes until the juices are bursting from the fruit. Add the vinegar then remove from the heat and set aside.
Preheat a charcoal or gas barbecue and if using charcoal when the coal has a coating of white ashes, push the ashes on one side of the barbecue. Then place the woodchips into a tin foil container .
Cut a piece of aluminium foil and fold to fit into the foil container on top of the woodchips, then use a sharp knife to pierce the aluminium foil 6 – 8 times, to allow the smoke to permeate through to the fish.
Brush the pierced foil with some olive oil then add the mackerel, season with rock sea salt and pepper.
Start the smoking process by placing the foil container on the direct heat on the barbecue for 4 – 5 minutes until the woodchips begin to smoke, then move on to the indirect heat (i.e the cooler side of the barbecue) and allow to smoke for approximately 10 minutes.
To Serve: Remove the fish from the foil and place 2 fillets overlapping per plate, serve with redcurrant sauce.