Heat your oven to 200°C/Fan 180°C/Gas 8. Remove the chicken from its wrapping and remove the giblets (save them for making homemade stock – see our tip). Pat the chicken dry and pop it into a roasting tin.
Add 1 tbsp wholegrain mustard to a small bowl and drizzle in the honey. Finely slice the parsley stalks, setting the leaves to one side. Add the parsley stalks to the bowl. Season with a pinch of salt and pepper and stir to combine.
Brush half the honey and mustard mixture all over the chicken. Slice the lemon in half. Pop the unpeeled garlic cloves inside the chicken cavity, and add 1 lemon half, setting the other half aside. Cover the chicken with foil, crimping it to the sides of the tin. Slide into the oven to roast 1 hr 15 mins.
When the chicken has roasted for 1 hr 15 mins, remove the foil. Brush a little more of the honey and mustard glaze over the chicken and slide it back into the oven, uncovered, for 5 mins. Remove from the oven again, brush the chicken with the remaining glaze and then roast for 5-10 mins, till the skin is golden and sticky.
Take the chicken out of the oven and check if it’s cooked through by poking a skewer or knife into the fattest part of the leg. The juices should run clear. If not, roast for 10-15 mins more. When cooked, lift the chicken out onto a plate or board, loosely cover with foil and rest for 30 mins.
While the chicken is resting, scoop the garlic cloves out of the cavity with a spoon. Squeeze the roast garlic flesh out of the skins and crush it into a paste. Add the garlic paste to a small bowl. Pour in 1 tbsp thyme oil and squeeze in the juice from the reserved lemon half. Finely chop the parsley leaves and add them to the bowl. Add a little salt and pepper and stir well.
Carve the chicken and serve it drizzled with plenty of the lemony thyme and garlic dressing.