Mix the flour, baking powder, bicarbonate of soda, spices and lemon rind together in a mixing bowl. Add the butter and rub in with your fingertips until the mixture resembles fine breadcrumbs.
Stir in the sugar, add the syrup then mix together first with a spoon then squeeze the crumbs together with your hands to form a ball.
Shape the dough into a log then slice into 12. Roll each piece into a ball and arrange on 2 large greased baking sheets, leaving space between for them to spread during cooking.
Cook one baking sheet at a time in the centre of a preheated oven, 180°C (350°F), Gas Mark 4, for 8–10 minutes or until the biscuit tops are cracked and golden.
Leave to harden for 1–2 minutes then loosen and transfer to a wire rack to cool completely. Store in an airtight tin for up to 3 days.