Mix the buttermilk with the lemon rind, garlic, celery salt, pepper, paprika, mustard and herbs. Mix well, pour over chicken. Marinate for 3 hours or overnight.
Preheat the oven to Gas 7/220C.
Place the flour on a plate, remove the chicken from the marinade and roll the pieces in the flour. Place the drumsticks on a lightly oiled baking tray and spray with a little oil. Roast for 15 minutes in the oven then spray again with a little more oil.
Cook for a further 15-20 minutes until the chicken is golden and no longer pink in the centre. Serve with oven chips and ketchup.