PREPARE AHEAD - Cover the prepared chicken with clingfilm. Pile the prepared vegetables in a bowl and cover. Both can be kept in the fridge for up to 24 hours. However, remember that the longer the chicken is kept before cooking, the more the garlic flavour will develop. Make sure that the chicken is at room temperature before roasting.
Preheat the oven to 200°C/180°C fan/Gas 6. You will need a large roasting tin for the chicken, large enough to hold the vegetables in a single layer, as well as the chicken. Loosen the skin from the neck end of the chicken over the breasts – use your finger to free the skin from the flesh.
Mix the butter and garlic together and season with salt and pepper. Spread the garlic butter under the skin over the breasts. Stuff the cavity with the lemon wedges and thyme sprigs then place the chicken in a roasting tin. Season with salt and pepper and roast for about 20 minutes.
Toss the prepared vegetables in oil and season with salt and pepper. Scatter the vegetables around the chicken in the roasting tin. Return to the oven for 1 hour or until the vegetables are golden and the chicken is tender, basting from time to time with the juices. Transfer the chicken to a carving board to rest and spoon the vegetables into a dish and keep warm. Sit the roasting tin on a low heat on the hob, sprinkle in the flour and whisk, scraping up the sides of the tin. Blend in the wine and stock with the whisk and bring to the boil, stirring until thickened. Carve or joint the chicken and serve with the vegetables and gravy, garnished with parsley.