In a bowl rub together the breadcrumbs, garlic, rosemary, butter, pinenuts and chopped bacon if using. Press half of the mixture onto the meaty side of each lamb rack and place on a roasting dish. Beside them place the four tomatoes.
Roast at 220°C for 25-30 minutes. If you like your lamb well done cook for 35 minutes. Remove from the oven and set the lamb aside.
Place the baked tomatoes into a saucepan and squash with a wooden spoon or masher. Remove any chunky core pieces. Add the stock, rosemary and olives and simmer for 5 minutes. Season well with salt and pepper.
Carve each loin in half.
Serve lamb with the squashed tomato and olive sauce and your favourite potatoes.