Cook the beans in a pan of boiling salted water for 6-8 mins until just tender. Drain and quickly cool under cold running water. Set aside.
Heat the oil in a large pan on the barbecue, then add the garlic and cook quickly until lightly browned. Add the beans, stir well, cover and leave to reheat. Meanwhile, cook the tomatoes on the grill bars until softened and slightly browned. Tip the beans into a serving bowl and top with the tomatoes. Sprinkle with a little sea salt and serve.