Preheat the oven to 180°C / 160°C Fan / Gas Mark 4.
To make the croutons: place the slices of baguette on a baking tray & drizzle with olive oil. Place in the oven & bake for 8- 10 minutes. Set aside to cool & then roughly crush them.
To make the Marie Rose sauce, mix all the ingredients together.
Place the celery, cucumber, radishes & prawns in a bowl, add the Marie Rose sauce & stir gently to combine.
Take the outer leaves of the little gem lettuces & divide them between two glass serving dishes. Shred the remaining lettuce & place in the base of the dish, and spoon the Prawn Cocktail mixture over the top. Sprinkle with the crushed croutons and serve.