My top tips are to make sure your tomato is nice and ripe and keep any juice when slicing it. For extra flavour use a little of the oil from the anchovies on half of the bread.
Prepare all the ingredients. Cut the bread in half. If you are using a large roll remove some of the filling with your fingertips.
Drizzle both halves of the bread generously with olive oil or oil from you anchovies if you have some spare. Spoon over any saved tomato juice if you have any.
Layer on the tomatoes followed by the cucumber and season. Add the radish and olives followed by the sliced boiled eggs.
Top with the tuna and anchovies and the remaining piece of bread. Press down firmly and wrap in greaseproof paper and foil. Allow to rest in the fridge for half an hour before eating.