Bring a large pan of salted water to the boil. Peel and crush the garlic. Halve the cherry tomatoes.
To make the chilli crumbs, heat half the oil in a large frying pan over a low to medium heat. Add the breadcrumbs and fry for 2 minutes, until turning golden. Add half the garlic and add chilli flakes and salt to taste. Cook for a further 1–2 minutes, until fragrant and crisp. Scrape out of the pan and set aside.
Cook the spaghetti for 10–12 minutes, until al dente. Add the remaining oil and garlic to the frying pan and fry over a low to medium heat for 1 minute. Then add the tomatoes and cook for a further 6 min, until beginning to break down.
Drain the pasta, reserving a mugful of the cooking water. Add the olives, capers and sardines to the frying pan – stir gently to warm through. Toss the pasta through the sauce, loosening with a little of the cooking water if necessary. Check the seasoning and add lemon juice, to taste. Serve the spaghetti with a sprinkling of parsley and breadcrumbs.