Add the potatoes to the bottom of a large casserole dish, drizzle over the olive oil and season with salt and pepper. Add the onion between the potatoes and sprinkle over the thyme.
Marinade the chicken in all the ingredients under the 'chicken marinade' section. Leave to rest for 45 minutes or overnight.
Preheat oven to 220 degrees, Gas Mark 7.
Add the chicken to the casserole dish and bake in the oven for 1 hour 20 minutes. (Check at 1 hour).