Preheat the oven to 150C/Gas 2. Select a heavy-based, ovenproof pan that will hold the lamb shanks quite closely together. Season the shanks and put them in a colander. Throw the flour over them and shake it around over the sink.
Heat half of the oil in the pan and sear the shanks on all sides until golden brown. Take the meat out and set aside. Fry the onions, celery, carrot and garlic, stirring from time to time. After 5 minutes, turn the heat down and cover.
After 10-15 minutes of on-off stirring, the veg will have softened nicely. Put the meat back in and add the wine and the bay leaves. Let the wine reduce by a third, then tip in the tomatoes, along with enough stock so that the liquid just about covers the shanks.
Add the olives and season.
Pour in the rest of the oil, cover and place in the oven for 2-3 hours, until the meat chunks are coming away from the bone. Take the dish out of the oven and let it sit for 15 minutes with the lid on.
Cook the pasta according to the directions.
To make the gremolata, mix the chopped parsley, lemon zest, garlic, and some seasoning.
Drain the pasta, return it to the pan and ladle in all of the veg and juice to coat it nicely.
Toss gently and tong into a serving dish. Put the shanks on top, add a ladle or two more of the sauce and sprinkle with gremolata.