Preheat the oven to 200C/400F/Gas 6.
For the roast chicken, mix the crème fraîche and watercress together in a bowl and season with salt and freshly ground black pepper. Spoon the mixture into a piping bag.
Place the chicken into a roasting tin. Slide your hand up under the skin of the chicken and place the nozzle of the piping bag under the skin. Squeeze the filling mixture in, smoothing down over the breast and leg.
Rub the butter and olive oil over the bird and season with salt and freshly ground black pepper. Lay six slices of bacon over the breast of the chicken.
Transfer the chicken to the oven and roast for 20 minutes per 450g/1lb, basting frequently. To check whether the chicken is cooked, push a skewer into the thigh at the thickest point. If the juices run clear the bird is done. If not, return to the oven for a further five minutes at a time. Remove from the oven, place onto a serving plate and set aside in a warm place for 15 minutes.
To make the gravy, place the roasting tin onto the hob and heat gently, stirring with a wooden spoon and scraping up all the bits from the bottom of the pan.
Add the plain flour and cook, stirring, for 1-2 minutes.
Add the wine and simmer until reduced by half. Add the stock and simmer for five minutes. Season, to taste, with salt and freshly ground black pepper, then pass the gravy through a sieve into a jug and keep warm until ready to serve.
Wrap the remaining bacon slices around the chipolata sausages. Place onto a baking sheet and bake in the oven for the last 15 minutes, while the bird is resting.
Meanwhile, for the vegetables, place the potatoes into a large saucepan. Cover with water, add a pinch of salt and bring to the boil. Reduce the heat and simmer for 3-4 minutes. Drain into a colander and shake around a little to rough up the edges.
Place a deep roasting tin onto the heat and pour in the fat. Add the potatoes and fry on each side until they start to brown. Sprinkle with salt, then transfer to the oven and roast for 50 minutes-an hour, turning halfway through the cooking time, until golden-brown and crisp.
Cook all the remaining vegetables in boiling salted water until just tender, then drain and refresh in iced water. When all the vegetables are cooked and have been cooled, place them on a large plate in the fridge, covered.
For the bread sauce, stud the onion all over with the cloves, then place into a saucepan along with the bay leaf, peppercorns and milk. Bring to the boil, then remove from the heat and allow to cool and infuse.
Remove the onion, bay leaf and peppercorns and discard. Add the breadcrumbs to the pan and stir. Return the pan to the heat and heat very gently for 5-10 minutes, stirring occasionally until the breadcrumbs have absorbed all the liquid. Stir in the butter and season, to taste, with salt and freshly ground black pepper.
When you're almost ready to serve the roast, make the game chips. Place the vegetable oil into a deep, heavy-bottomed saucepan and heat until a small cube of bread sizzles and turns golden when dropped into it. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
Carefully place the potato slices into the hot oil and deep fry for 1-2 minutes until golden-brown. Remove from the oil with a slotted spoon, drain on kitchen paper and season with salt and freshly ground black pepper. Pile the game chips onto the chicken platter.
Bring a large pan of water to the boil. Take the vegetables out of the fridge and drain, then place into the saucepan of boiling water and cook for 30-45 seconds until warmed through.
Drain the vegetables and return to the pan. Add the butter, season with salt and freshly ground black pepper and stir well to coat.
To serve, place the vegetables and roast potatoes into serving dishes. Pour the bread sauce into a serving jug. Carve the chicken, place onto serving plates and pour over the gravy.