Cook the spaghetti in plenty of salted water until al dente. Meanwhile make the sauce.
In a large pan on medium heat cook the garlic in oil until sizzling. Add the tomatoes, coat in oil and cook for 5 to 7 minutes. When they start softening, push against the side of the pan so they will release their juices. Season with salt and chilli.
Add the crab, coat in the sauce and cook for 3 to 4 minutes. Adjust seasoning and add half of the parsley. Make sure the sauce does not get too dry; in so, add a bit of water. Remove garlic.
Drain the spaghetti and add to the sauce, along with a few tablespoons of cooking water. Coat well in the sauce and cook all together for about 30 seconds.
Place on plates or transfer to a serving bowl. Sprinkle with the remaining parsley, drizzle with some more oil and serve.