Greek salad

Name: Greek salad
Ingredients: 50g/2oz black kalamata olives; 3 medium tomatoes, diced into 2cm/¾in cubes; 1 cucumber peeled, diced into 2cm/¾in cubes; 1 red pepper, de-seeded, diced; ½ red onion, sliced finely; 100ml/3fl oz extra virgin olive oil; 150g/5oz feta, diced; 1 small, firm cos lettuce, chopped into rough cubes lengthways; 1 generous sprig of oregano (or 2 tbsp dried oregano); 50ml/3 tbsp red wine vinegar