Place the whole chicken on a chopping board breast-side down.
Remove the backbone by cutting up one side from the base of the bird to the neck end, cutting right through the ribs attached to the backbone as you go.
Open the bird and cut along the other side of the spine (exactly as before) to remove it completely.
Now place the chicken skin side down, and press down firmly on the breast area with the palm of your hand to break the breast bone (this will flatten the bird).
Turn the chicken over and flip its legs inwards so that the bird lies as flat as possible.
Now transfer the flattened chicken, skin-side up, to a roasting tin lined with non-stick baking paper and coat with the piri piri sauce.
Leave to marinate in a cool place for 20 minutes. If you have the time, cover it with clingfilm and chill overnight.
Allow the chicken to come up to room temperature for 30 minutes before cooking.
Preheat the oven to 220°C / 425°F / Gas mark 7.
Cook at the top of the oven for 20 minutes, then baste with the cooking sauces within the tin.
Cook for a further 20-25 minutes, until cooked through with slightly charred skin.
The juices should run clear when the thickest part of the thigh is pierced.
Rest the chicken for 5 minutes before cutting into pieces and serving with a green salad, lemon wedges and oven the chips.