Preheat the over to 150 C, Gas 2.
Heat the oil in the flameproof casserole dish. Add the lamb and shanks and cook for about 7-10 minutes, until browned all over, turning halfway though. Transfer the lamb shanks to a dish, season generously with salt and set aside.
Add the onions and carrots to the casserole dish and cook for 3-5 minutes, until just browned. Add the garlic and anchovies, if using, and cook for 1 minute.
Season well and add the wine. Bring to the boil and cook for 1 minute.
Return the lamb shanks to the casserole dish and add the herb bundle, burying it in the liquid. Add water if necessary; the lamb should be almost completely submerged in liquid.
Cover and cook in the preheated oven for 2 hours, checking occasionally, to ensure the liquid does not reduce too much.
After 2 hours, top up with water if the liquid has greatly reduced, then add the potatoes and tomatoes and a good pinch of salt. Cook for 1 hour.
Remove from the oven, taste and adjust the seasoning if necessary. Remove the herb bundle before serving.