Cut small slits on one side of each sardine. Rub the lemon and oil mixture all over the sardines, rubbing well into the slits and body cavity. Cook the sardines on a preheated barbecue (or over a medium-high heat in a griddle pan) for 3 minutes each side, until cooked through and the flesh flakes away easily from the bone. Put the lemon halves, cut-side-down, next to the fish for the final 3 minutes of the cooking time. Tip: If buying the sardines from the fish counter in store, you can ask the fishmonger to gut the fish for you. Alternatively, insert a sharp knife into the base of each fish approximately 2cm (1in) from the tail, run the knife along the base finishing at the head. Open-out a little, then starting at the head end – run your thumb along the inside (wear disposable rubber glove, if you like) to remove the guts and discard. Rinse the cavity under cold running water to clean thoroughly. (If there are any scales on the fish remove by running a blunt knife over the skin, then rinse under running water.) Minimum life based on 'use-by' date of product. Average life based on last week's deliveries. Life guarantee shown based on delivery tomorrow with the Life guarantee starting the following day.