Heat the oven to 180C. Place the chicken in an ovenproof dish and arrange the lemon wedges round about. Drizzle liberally with olive oil and rub into the chicken skin. Season generously with salt and pepper. Roast for 45-50 minutes or until the chicken juices run clear. Baste 2 or 3 times during cooking.
To make the stuffing:
Fry the leek in some olive oil until soft and lightly coloured. Add the pancetta or bacon and fry for a few minutes. Add the garlic and herbs and fry for 2-3 minutes, stirring occasionally. Season and transfer to a large bowl – leave to cool completely.
Once this mixture is cool, add the pork sausagemeat to the bowl. Using your hands mix the whole lot together well. Add the breadcrumbs and egg and mix until it is all combined. You should be able to easily shape the mixture – if it is too wet add more breadcrumbs. Shape into little balls, about the size of a walnut. Arrange on a baking tray and roast with the chicken for about 20 minutes or until cooked through.
Once the chicken is cooked transfer to a plate and keep warm while you make the gravy. Put the roasting dish on the hob on quite a high heat and bring to the boil. Add a sprig of thyme and about a cup of water. Scrape all the bits from the bottom of the dish and bubble until reduced slightly. Check and adjust the seasoning. Strain through a sieve into a jug.
Serve the chicken, stuffing balls and gravy with potatoes and vegetables of your choice.