Heat the oil in a large high-sided frying pan, add the anchovies and fry gently for a minute or so. Stir through the tomato purée and chilli flakes, increase the heat to medium and fry, stirring, for a couple more minutes. Pour over the tinned tomatoes and stir in the ketchup, dried basil, pitted olives and capers. Bubble the sauce over a low heat for 5 minutes until thickened. Season well.
Meanwhile, cook the pasta in a large pan of salted water for 10 minutes or until al dente, drain well, return to the pan and fold through the sauce. Serve with warm garlic bread.