Bring a pan of salted water to a rapid boil and cook the trimmed French beans for two minutes then plunge immediately into iced, cold water to refresh. Drain and set to one side.

Wash and clean the potatoes. Place the potatoes in the pan and cover with cold water. Add a half teaspoon of salt and bring to a gentle boil, simmer until the potatoes slide of a small sharp knife. Plunge into cold water, cool and drain.

Halve the tomatoes and carefully cut out the core with a small sharp knife. Cut each tomato half into four pieces.

Remove the mackerel skin and carefully scrape of the darker brown meat along the centre of the fish. Break into chunks.

To make the dressing, crush the garlic on a heavy chopping board with the salt using the blade of a large cook’s knife, then chop to a pulp. Whisk together with the remaining ingredients and store in a sealed container in the refrigerator.

Arrange the Romaine lettuce leaves in bowls and add the picked watercress. Add the tomatoes, potatoes, French beans, and olives. Drizzle with dressing and top with torn basil leaves and mackerel. Halve soft-boiled eggs and add to the finished dish.