Put the couscous in a large bowl and cover it with cold water. Leave it for 30 mn and mix it regularly with a fork. When the water has been fully absorbed by the couscous add the lemon juice, salt and pepper.
Clean the tomatoes and remove the seeds. Cut the tomatoes and cucumber in very small dices. Add them to the couscous with the olive oil.
Cut the herbs in very small pieces and add them to the couscous. Put a plastic on the bowl and leave it in the fridge for at least 2 hours.