Preheat the oven to 220C. Mix together the butter, 15ml/1 tbsp of the chopped tarragon, the garlic and seasoning in a bowl. Spoon half the butter mixture into the cavity of the chicken.

Carefully lift the skin at the neck end of the bird from the breast flesh on each side, then gently push a little of the butter mixture into each pocket and smooth it down over the breasts with your fingers.

Season the bird and lay it, breast-side down, in a roasting tin. Roast in the oven for 45 minutes, then turn the chicken over and baste with juices. Cook for a further 45 minutes.

When the chicken is cooked, lift it to drain out any juices from the cavity into the tin, then transfer the bird to a warmed platter and keep warm.

Place the roasting tin on the hob and heat until sizzling. Stir in the flour and cook for 1 minute, then stir in the cream, the remaining tarragon, 150ml/14 pint water, the lemon juice and seasoning. Boil and stir for 23- minutes, until thickened.

Garnish the chicken with tarragon and lemon slices and serve with the sauce.