Mise en Place
First prepare the beans: put them to soak overnight in plenty of cold water. Next day, drain them and put in a pan with at least double their volume of water. Bring to the boil over a high heat and boil hard for 10 minutes (they will throw a creamy white scum). Drain in a colander, rinse in clean water and return to the pan.
Cook the beans: chop the carrot, celery, onion and 4 of the garlic cloves into a brunoise and put into the pot with the beans, the piece of bacon, one of the rosemary sprigs and the bay leaf. Cover with cold water, allowing a 2.5cm/1 in head above. Bring to a gentle simmer, stir and film the surface with olive oil. Cook very slowly for 2 hours. Remove from the heat and set aside.
Preheat the oven to its highest setting and brush the roasting pan with oil • Brush the racks of lamb with olive oil. Using a small sharp knife, score the fat in a diamond pattern and rub salt and pepper into the cuts and on both sides of the meat • Slice the remaining garlic cloves across into very thin slivers and strew them in the roasting pan. Scatter half the remaining rosemary leaves and half the thyme over the garlic and sit the lamb racks on the garlic, fat side downwards. Scatter the remaining rosemary and thyme on top of the meat • Chop the parsley and juice the lemon.