Clean the leeks and chop into 1/2" pieces.
Warm the oil in a shallow fire-proof dish and put in the leeks before it is too hot.
Add salt and pepper, cover the dish and simmer for 10 minutes.
Add the peeled halved tomatoes, the stoned olives, the juice and peel and cook slowly with the lid on for a further 10 mins.
Serve in the dish it has cooked in.
This dish is excellent served cold as a salad.