Preheat oven to 200°C or 180°C fan. Combine breadcrumbs, herbs, lemon rind, juice and egg in a bowl. Season and mix well. Push into cavity of chicken, securing legs together with string.
Combine butter and garlic. Starting with skin at tip of chicken breast, carefully separate skin from breast meat. Push garlic butter under skin.
Rub oil all over chicken skin and sprinkle with salt and pepper to taste.
Place chicken on a rack in a baking dish and scatter around potato. Roast for 1 ¼ hours, turning potato once, until chicken juices run clear and potato is tender. Serve chicken and potato with steamed vegetables and gravy.