Grilled mackerel with Mediterranean vegetables

Name: Grilled mackerel with Mediterranean vegetables
Ingredients: 1 unwaxed lemon, zest and juice; 1 small garlic clove, peeled and finely grated; 1 tbsp extra-virgin olive oil; pinch chilli flakes; 1 red pepper, deseeded and sliced into 1cm/½in thick strips; 1 yellow pepper, deseeded and sliced into 1cm/½in thick strips; 150g/5½oz cherry tomatoes, washed and left whole; 1 small red onion (about 40g/1½oz), thinly sliced; 1 tbsp olive oil; small bunch parsley, roughly chopped; small handful basil, roughly chopped; handful rocket; 80g/3oz stoned green olives, roughly chopped; 4 mackerel fillets (about 300g/10½oz total weight), deboned, skin left on; ½ tbsp olive oil