To make tomato salsa, preheat oven to 180C. Place tomatoes, garlic and thyme on a baking tray. Season generously with sea salt and freshly ground black pepper and drizzle with half the olive oil. Roast for 35-40 minutes. Cool, then transfer tomatoes and garlic to a chopping board and roughly chop. Transfer to a bowl, adjust seasoning, add red wine vinegar and remaining olive oil and combine well.
To make meat loaf, preheat oven to 200C. Melt butter and olive oil in a frying pan over medium heat. Add onion, garlic and celery and cook, stirring, for 5 minutes until softened. Add Worcestershire sauce and cook, stirring, for I-2 minutes. Transfer to a large bowl. Add pork, veal, bread, parsley and egg and season generously with sea salt and freshly ground black pepper. Mix to combine with your hands.
Place pancetta slices, overlapping, in a 5-cup terrine mould. Place half the meat loaf mixture in the mould and press down. Add eggs and cover with remaining meat loaf mixture. Place mould in a baking tray. Pour boiling water into the tray so that it comes halfway up the sides of the mould.
Bake in a preheated oven at 200C for 50 minutes or until a meat thermometer registers 68C when inserted in the middle. Remove from oven and allow to cool, covered with foil, for 5 minutes. Serve either hot or cold with tomato salsa, green salad, bread and butter pickles and English mustard.