For the salad:
For the Marie Rose sauce:
Make the Marie Rose sauce first. Deseed the tomato and chop it into small, pea-sized pieces. Put two teaspoons of these in a bowl and add the rest of the sauce ingredients. Mix well.
Rinse the prawns and squeeze them dry. Then chop the celery sticks to the same size as the tomatoes, and put the prawns and celery in a second bowl. Add the Little Gem lettuce and the mixed herbs. Then pour in the Marie Rose sauce and gently stir the salad to bind everything together.
Prepare the serving ingredients. Cut the tomatoes into wedges and season them with Maldon salt; cut the lemon into four wedges lengthways. Shake the olive oil and lemon juice together to make a dressing, and use it to dress the iceberg lettuce. Divide the iceberg between the serving plates and set the prawns on top. Then garnish with the ripe tomato pieces, the lemon wedges and a few fresh herbs. Serve immediately.