Peel and grate the ginger and garlic, then mix with the oil and lemon juice.
Rub the chicken with this mixture and marinate for a couple of hours.
Mix the spices with yogurt. Place the chicken into a freezer bag and pour over the spiced yogurt. Tie the bag, then massage the chicken well through the bag.
Chill for at least 2 hours, preferably overnight. Occasionally squeeze the marinade around the bag to cover the chicken well (through the bag!).
Preheat the oven to 200°C. Remove the chicken from the fridge and place them in a roasting tin together with the marinade. Roast for about 35 minutes until the chicken turns light brown.
Finish off the cooking on the barbecue - cook it for 5-10 minutes until lightly charred.
Serve warm.