Pre-heat oven to 150 degrees C (gas mark 2).
Heat the olive oil in a roasting tray on the cooker over medium-high heat.
Toss shanks with flour to coat well.
Sear the shanks in hot oil until browned.
Remove from tray and set aside.
Add the leek, celery, carrot, onion, and garlic to the roasting pan.
Cook until softened.
Add the bay leaf, peppercorns, thyme and rosemary sprigs.
Add the red wine and chicken stock
Turn heat up and bring to a simmer.
Taste and season accordingly.
Add the lamb shanks on top of the vegetables.
Cover the roasting pan tightly with foil.
Place into the preheated oven.
Bake until the meat is tender.
Remove the bay leaf and herbs.