Arrange the tomatoes close together, cut side up, in a roasting tin. Scatter over the chopped garlic and basil, drizzle with 1 tablespoon each of the oil and balsamic vinegar and season well with salt and pepper. Cook in a preheated oven, 220°C (425°F), Gas Mark 7, for 15 minutes.
Meanwhile, cook the pancetta slices in a preheated hot griddle pan for about 2 minutes, turning once, until crisp and golden. Transfer to a plate lined with kitchen paper until needed.
Quickly sear the scallops for 1 minute in the hot griddle, then turn them over and cook for a further minute on the other side until cooked and starting to caramelize. Remove, cover with foil and leave to rest for 2 minutes.
Meanwhile, cook the artichoke hearts for about 2 minutes until hot and charred.
Toss the lamb's lettuce with the remaining oil and balsamic vinegar and arrange on serving plates. Top with the artichokes, tomatoes, crispy pancetta and scallops. Serve immediately.