Thinly slice the leek and the garlic.
Peel and roughly chop the parsnip, swede and celeriac.
Heat the oil in a large casserole dish and brown the chicken all over, for about 8 minutes, then transfer them to a plate.
Add a drop more oil to the dish, then sauté the leek for 5 minutes. Add the chopped veggies and marjoram. Add the wine, let it bubble and reduce it by half.
Place the chicken on top of the veggies, then pour in enough water to just cover the veggies (not fully the chicken). Crumble the stock cube into the jus.
Add the rosemary, bay leaf and lemon slices. Season with salt and pepper.
Bring to the boil, put the lid on and gently simmer over low heat for about 45 minutes.
Serve warm.