Grilled mackerel with cucumber and tomato salad

Cut cucumbers into quarters lengthwise. Chop into segments about five millimetres thick and toss with a few pinches of salt. Place in a colander over a bowl for 20 minutes so they lose some water, then transfer to a clean cloth and wring out remaining water. In a bowl, mix cucumber with tomatoes, 3 tbsp olive oil, lemon juice, both vinegars and parsley. Season with salt and pepper to taste. Cut each mackerel fillet down the middle on either side of the bone line, leaving any small bones in that thin strip. Heat remaining olive oil on a grill or in a pan until it is just smoking. Fry mackerel for 20 seconds each side and serve with salad.