1. Cook the pasta in a large saucepan of salted boiling water according to the package instructions.

2.Meanwhile, put the lemon juice and chile in a bowl with half the basil and cilantro and salt and pepper to taste. Whisk well to mix, then whisk in the oil and mayonnaise until thick. Add the shrimp and gently stir to coat in the dressing.

3. Drain the pasta into a colander; and rinse under cold running water until cold. Let drain and dry, shaking the colander occasionally.

4. Halve, pit and peel the avocado, then cut the flesh into neat dice. Add to the shrimp and dressing with the pasta, toss well to mix and taste for seasoning. Serve immediately, sprinkled with the remaining basil and cilantro.