Grate the cucumber into a bowl then squeeze it with your hands to remove as much juice as possible.
In a food processor, whizz the yogurt, mint and coriander together until blended. Tip into a bowl and stir in the cucumber. Cover with cling film and chill until you are ready to serve.
To serve, preheat the oven to 200C/gas 6/fan 180C. Cut the naan into long triangles and arrange on 2 large baking sheets. Brush them with oil on one side and sprinkle over a little paprika and salt. Bake for 8-10 minutes until crisp and golden. Season the raita with up to 1 teaspoon of salt (see tip) and lemon
juice to taste. Serve on a platter with fresh tomato chutney and dippers.