Preheat your oven to 200°C (fan-assisted) or 220°C conventional. While it heats, take the chicken out of the fridge and let it sit at room temperature for 20 minutes. Pat the skin completely dry with kitchen paper — this is the secret to that golden, crisp skin. You'll feel the paper absorbing any moisture, and the skin should look matte, not shiny.

Make the herb butter. In a small bowl, mash the softened butter with the minced garlic, thyme, rosemary, parsley, salt, and pepper. Stir until everything is evenly distributed. The butter should be fragrant and slightly speckled green from the herbs.

Season the chicken. Gently loosen the skin over the breast and thighs using your fingers — you'll feel it separate easily. Push about half the herb butter directly under the skin, spreading it evenly. Rub the remaining butter all over the outside of the chicken. The surface should look glossy and well-coated.

Stuff and truss. Stuff the lemon halves and onion quarters into the cavity of the chicken. Tuck the wing tips under the body and tie the legs together with kitchen string. This keeps the shape neat and helps the chicken cook evenly. The bird should look compact and tidy at this stage.

Prepare the roasting dish. Scatter the chopped carrots and celery in the bottom of a large roasting tin. Pour in the chicken stock. Place the chicken on top of the vegetables, breast side up. Drizzle with the olive oil, then give the bird a final light sprinkle of salt. You'll see the vegetables and stock sitting below, ready to create a natural jus.

Roast the chicken. Place the tin in the preheated oven. Roast for 1 hour 15 minutes to 1 hour 30 minutes, basting every 20 minutes with the juices from the bottom of the tin. The skin will gradually turn a deep golden brown, and you'll hear it sizzling. It's ready when a thermometer inserted into the thickest part of the thigh reads 74°C, or when the juices run clear when you pierce the thigh with a knife. The aroma of roasted herbs and garlic will be unmistakable.

Rest before carving. Lift the chicken onto a carving board, tilting it slightly to let the juices from the cavity run into the roasting tin. Cover loosely with foil and rest for 15 to 20 minutes. This step is non-negotiable — the meat relaxes and reabsorbs its juices, so it doesn't spill all over your board when you carve. You'll notice the skin stays crisp even as it rests.

Make the pan jus. While the chicken rests, strain the vegetables from the roasting tin and discard them. Place the tin on the hob over medium heat. Scrape up any browned bits with a wooden spoon, then simmer the remaining liquid for 2 to 3 minutes until it thickens slightly. Pour this rich jus into a warm jug for serving.

Carve and plate. Slice the breast meat against the grain, then separate the legs and thighs. Arrange the pieces on a warm platter, pour a little jus over the top, and garnish with a few fresh herb sprigs. The slices should be moist and glistening, with a thin strip of crisp skin on each piece.