Rinse the chickens and pat dry. Cut each chicken in half so you have four pieces. Cut off the wing tips and cut a little way into the bone joints so they crack open and flatten to help the chicken cook evenly. Make a couple of slashes where the meat is thickest to be sure that it cooks all the way through.
To make the marinade, cut the lemon in half and squeeze the juice into a bowl that will fit the chickens. Throw in the lemon halves, garlic, oregano, paprika and then the chickens, scattering with the coarse salt. Turn it all together well and massage into the chickens. Leave covered (but not in the fridge) for at least half an hour until the chicken has taken in the salt (if you're leaving it longer you'll need to put it in the fridge).
Heat the barbecue with a grill 15cm (6in) from the hot coals. To make the basting sauce, pulse the chillies and garlic to a rough paste in a food processor (or use a mortar and pestle). Heat the butter and oil with the paste in a small pan until it is sizzling and you start to smell the garlic. Add the lemon juice, bay leaf, port and whisky and let it bubble up for 5 minutes, then remove from the heat. Taste and add more ground piri piri if you like.
Shake the chickens out of the marinade and place, skin side up, on the grill. Don't allow the skin to burn. Turn the chickens when the first side is cooked. After 25 minutes or so, when they're almost ready, start basting with the piri piri. Baste a couple of times on each side. Cut each chicken half into four (it's nicer to serve this way and you can check that the bits closer to the bone are cooked) and drizzle with the rest of the piri piri sauce.
Recipe from Piri Piri Starfish by Tessa Kiros, published by Murdoch Publishing, £22·50. Click here to buy book