Toss the veal shanks in the seasoned flour. Heat some oil in a large, heavy-based pan and cook the shanks until browned all over, then remove from the pan.
Heat more oil in the pan if necessary and add the onion, garlic, celery, carrot and a pinch of sea salt and cook over medium heat until the onions are soft.
Stir in the olives, lemon and orange zests, wine, tomato, stock, bay leaves, thyme and browned shanks.
Simmer very slowly, covered, for 1 hour. Remove the lid and simmer uncovered for a further 45 minutes, or until the meat is falling off the bone.
Bring 1.25–1.5 litres (5–6 cups) water to the boil in a saucepan. Add some sea salt and pour in the polenta, whisking constantly, until it is completely incorporated.
Reduce the heat and cook for about 40 minutes at a gentle simmer, stirring from time to time with a wooden spoon.
Stir in the butter and Parmesan, check for saltiness and give a good grind of pepper.
Add peas to the osso bucco and cook for five minutes, or until the peas are tender.
Check the seasoning and add more sea salt if necessary.
Place a spoonful of polenta on the side of four large bowls, spoon the shank mixture on and give a good grind of pepper and a squeeze of fresh lemon.