Light a lidded barbecue. Let the flames die down and the coals turn ashen, then mound the coal up on one side. If using a small barbecue, you will have to remove the grills and place a sturdy roasting tin on the floor of the barbecue, next to the coals – this will give you space to close the lid once the chicken is in. If you have a large barbecue, the chicken can sit directly on the grills (or on a tray on the grills, so that it doesn’t topple over.)
To make the rub, mix all the ingredients together with a good grinding of black pepper. Drizzle the chicken with the oil, sprinkle over the rub and massage it into the skin, making sure you get into all the nooks and crannies, even inside the cavity.
Use a can opener to take off the top of the can of beer. Pour out half the beer (tip into a glass to drink!) and leave the rest in the can, as it will keep the chicken moist while it cooks. Pop the chicken onto the can, legs down, so that it looks like it is sitting upright with the can in its cavity. Stand the chicken and can upright on the barbecue, either in the roasting tin or directly on the grill, on the side with no coals. Close the lid and cook for 1 hr 20 mins until the chicken is browned, the meat tender and the juices run clear. If the juices aren’t clear, cook for a further 10 mins, then check again. (To cook in the oven, heat to 200C/180C fan/gas 6. Sit the chicken on a baking tray, place in the bottom of the oven, and follow the same cooking time.)
Remove the chicken from the barbecue, cover lightly with foil and leave to rest for 20 mins before serving.