Cook the spaghetti in a pan of boiling salted water following pack instructions until just tender, with a little bite. Drain well, reserving a large mugful of the cooking water. (If the pasta clumps together while draining, pour over a little of the reserved water and gently shake apart using tongs.)

When the pasta has about 5 mins left, heat the rapeseed oil in a large, deep frying pan over medium heat. When the oil is shimmering, cook the onion, parsley stalks and a pinch of salt for 8-10 mins until softened and golden.

Add the garlic and tomatoes, and cook for 2-3 mins more. Tip in the mussels and prawns, turn up the heat to high and cook for 2 mins. Carefully pour in the ale (it should bubble up considerably), then cover with a lid and turn the heat down slightly. Cook for 3 mins, or until all the mussels have opened (discard any that remain closed) and the prawns are pink. Add the samphire, cooked spaghetti and remaining pasta cooking water, the parsley leaves, lemon zest and juice, and butter. Toss well to combine and season to taste. Serve directly from the pan, or tip onto a serving platter.