Place the chicken fillets on a foil-lined grill pan and brush with half the lemon juice. Season with salt and freshly ground black pepper and cook under a medium-hot grill for 20 mins, turning a few times.
Place the courgettes and peppers in a bowl with the rest of the lemon juice, olive oil, mixed herbs and chopped capers. Season with salt and freshly ground black pepper and spread on the grill pan around the chicken.
Grill the chicken, courgettes and peppers for a further 15-20 mins until the chicken is cooked through and the vegetables are lightly charred in places. Serve with salad.
Notes
If the chicken fillets are quite thick, butterfly them by cutting nearly all the way through each fillet and opening and flattening out the flesh – this will help to cook them quickly and evenly