Grilled Tuna Skewers with Green Olive Relish

800 grams tuna steaks

Marinade
4 tablespoons olive oil
finely grated zest 1 lemon
2 cloves garlic, crushed
1 teaspoon fennel seeds, toasted and roughly ground
freshly ground black pepper

Relish
½ cup stuffed green olives, finely chopped
3 anchovy fillets, finely chopped
1 tablespoon capers, roughly chopped
1 teaspoon finely grated lemon zest
1 clove garlic, crushed
1 tablespoon chopped flat-leaf parsley
2 tablespoons olive oil
1 tablespoon lemon juice
sea salt and freshly ground black pepper

To cook
bay leaves
2 lemons, thinly sliced and halved

13 cm wooden skewers, soaked in water