Olives that are not pitted have more flavour. The easiest way to pit them is with an olive or cherry stone remover. Place the seedless olives in a bowl.
Shred the mint with your hands. Wash the celery, cut the stalks and leaves into small pieces. Chop the chilli finely, removing the seeds beforehand. Cut garlic into coarse slices if you want to remove it later, otherwise you can chop or press it.
Mix mint, celery, chilli, garlic and olives and sprinkle evenly with lemon juice and olive oil. Cover with clingfilm and leave to marinate in the refrigerator for at least two hours.
Before serving, remove the garlic if you so desire and season with salt. Serve with fresh white bread.