Combine the onion, vinegar, oil, olives and herbs in a medium bowl.

Boil the potatoes in the base of a steamer for 10 mins. Add the eggs (top up with boiling water from the kettle if they’re not submerged). Tip the green beans into a pan and put the steamer on top, then cook for 8 mins more.

Remove the potatoes and eggs from the steamer, but don’t drain. Add the salmon to the water and cook for 5 mins. Stir the warm potatoes into the dressing.

To serve, divide half the lettuce between two plates (or pile onto one platter) along with half the green beans and tomatoes, then spoon half the dressed potatoes on top. Remove and discard any skin from the salmon, then flake half the fish over the salad. Peel one egg, halve and serve one half over each salad. Chill the remaining ingredients for the next day to eat cold. Will keep covered and chilled for up to a day.