Bring a large pan of water to the boil and add the spaghetti. Meanwhile, in a frying pan, heat the olive oil over a medium heat and add the sliced garlic and anchovies. Fry for a couple of minutes but do not let the garlic brown. The anchovies will begin to 'melt'.
Add the tinned tomatoes, olives and capers and simmer for 5 minutes. Taste for seasoning. Add salt if required and pepper.
When ready, drain the spaghetti reserving a cup of cooking water. Add the pasta to the sauce with a little of the cooking water to loosen. Check for seasoning.
Serve in bowls drizzled with olive oil and optional torn basil leaves.