Cut the eggs into slices. Drain the tuna, but not too dry as no more oil is added. Cut the spring onions into fine rings and finely chop the parsley, add both. Add the capers or simply leave them out. Mix the yoghurt with the mayonnaise and the spices, vinegar and Worcestershire sauce. Spread everything over the egg and tuna mixture and stir carefully so that there is no pulp.