Cook the spaghetti in a large pan of boiling salted water according to the packet instructions, then drain, reserving a mugful of starchy cooking water.
Place a large frying pan on a medium heat and drizzle in the oil from the sardine tins. Add the chilli flakes, finely grate in half the lemon zest, then add the capers.
Peel the garlic, then finely slice with the sun-dried tomatoes and add to the pan.
Using a speed-peeler, peel thin slices of courgette into the pan, then season to perfection with sea salt and black pepper.
Pick the parsley leaves and put aside, then finely chop and add the stalks to the pan and cook for 5 minutes, stirring regularly.
Lay the sardines in between the courgette, cover and cook for a final 5 minutes. Meanwhile, finely chop the parsley leaves.
Tip the drained spaghetti into the courgette pan, add the parsley leaves and toss together gently, loosening with splashes of cooking water to create a silky sauce.
Divide between bowls and serve with the remaining lemon cut into wedges for squeezing over.
