Remove the steaks from the fridge at least 20 minutes before cooking to bring up to room temperature. Transfer to a plate, cover and use when required.To prepare the marinade; in a large bowl mix all the ingredients together. Pour the marinade into a shallow non-metallic dish. Place the steaks in the marinade mixture and coat well on both sides. Cover and refrigerate for 2 hours, or if time allows overnight.Remove the steaks from the marinade (discard the marinade) and cook under a preheated moderate grill or on a prepared barbecue according to your preference, or until any meat juices run clear.Remove the steaks from the pan, transfer to a warm plate, cover with foil and rest for a few minutes.Serve with steaks an avocado salad and potato wedges.