Place the orange juice, soy sauce, sugar and rosemary in a pan, bring to the boil. Over a low heat, reduce to approx. half the amount.
To grill the meat
Salt the meat and rub well by hand. Charcoal/gas/electric grill: Cover and grill the meat over/on a low heat (approx. 150 °C for approx. 90 mins., turning the meat occasionally and brushing with the glaze.