Put the olive oil in a wide shallow pan and gently heat the pepper for a couple of minutes. Tip in the drained spaghetti and 2 tbsp of the cooking water. Stir a few times, then add the cheese and toss. It should come together to make a creamy sauce that coats the pasta. Add the crab and toss briefly to warm through. Serve on warm plates with an extra sprinkle of pepper.