Finely slice the tomato. Chop the onion, the bell peppers, and green chillies into small pieces. Place these in a bowl. Add the sweet corn. Pour the red wine vinegar and the olive oil into the bowl. Mix in the oregano, black pepper powder, and salt. Add the coriander leaves mix gently. Transfer the mixture to a serving dish. Pour a little olive oil on the top and garnish with the coriander leaves.