Cook the pasta in a large saucepan of boiling water according to the packet instructions, adding salt to flavor and some oil to stop the pasta from sticking, if desired.
Meanwhile, put the oil in a large saucepan (that has a tight-fitting lid) over medium heat. Add the shallots and gently fry until softened, stirring from time to time, 8 to 10 minutes. Add the garlic and chiles and cook for a couple minutes more.
Add the prawns and cook for 1 minute, stirring occasionally. Add the clams and white wine, bring to a boil and then cover with a lid. Cook until the clam shells have all opened (discard any that don't) and the prawns have turned from grey to pink, 4 to 5 minutes.
Once the pasta is cooked, drain well, tip it in on top of the shellfish and mix together well. Stir the chopped parsley through and season to taste with sea salt and black pepper.
Pile into serving bowls, drizzle with an extra bit of olive oil, scatter the arugula over, top with a good grinding of black pepper and serve each bowl with a wedge of lemon.
It's important to wash clams in their shells thoroughly before cooking. Ideally, they should be soaked in cold water for an hour before cooking. Discard any that remain open when tapped.