For the marinade, mix all the
ingredients together in a bowl. Place the
steaks in a shallow dish, pour marinade
over to coat the meat completely. Cover,
chill and leave to marinate overnight.
Scrape the marinade off the steaks
and rub each steak with a drop of
sunflower oil. Heat a griddle pan until
very hot, then rub the steaks with the
reserved lemon half and cook with the
rosemary sprig for 3-4 mins each side
for medium-rare, 1 min longer if you
prefer it cooked more. Rest for 5 mins
before serving with mash or chips.