Cook the pasta according to the instructions on the packet. Drain, and keep warm under a lid.
Meanwhile, thinly slice the leek. Using a Julienne peeler cut the courgette into long strips. Finely chop the garlic. Cut the sausages into 1 cm pieces.
Heat the oil a frying-pan and gently sauté the leek for 5 minutes. Add the garlic, sausages and courgette. Season to taste. Add the lemon juice and sauté under a lid for a further 5 minutes or so.
When the vegetables are tender and the sausage pieces have warmed through, mix in the pasta and olives.
Serve warm with chopped parsley leaves and plenty of ground pepper.