Preheat the grill to high. Cut the tomatoes in half, then place them, cut-sides up, on a heatproof dish. Sprinkle generously with freshly ground black pepper and trickle the oil over them. Grill the tomatoes for 4–5 minutes or until browned on top but still firm. Turn off the heat and leave them under the grill to keep warm while you prepare the rest of the meal.
Meanwhile, cook the linguine in a large saucepan of lightly salted boiling water for 10 minutes, or according to the packet instructions, until tender but still firm.
Put the chilli, cucumber, lemon zest, chives and fennel or dill in a large serving bowl and mix together thoroughly. Add the crabmeat and mix together lightly so the crabmeat doesn't break up too much.
Drain the cooked pasta, add it to the crab mixture and toss together. Add the tomatoes and their juices together with the rocket and mix lightly, taking care not to break up the tomatoes. Serve at once, with lemon wedges to squeeze over the top.