Heat the oven to 180C/fan160C/gas 4. Line several baking sheets with baking parchment or non-stick sheets. Warm the butter, sugar and golden syrup in a large saucepan over a medium heat until the butter has melted. Stir in the flour, bicarbonate of soda, oats, cinnamon, dried fruits and ginger, then the water and finally the egg. Leave to cool until easy to handle.
With dampened hands, shape the mixture into 18 large balls, then flatten them onto the baking sheets – allowing plenty of space for spreading – and bake for 15-20 mins until golden. (This will give a soft, chewy cookie. For a crisper one, reduce the heat to 160C/fan140C/gas 3 and bake for a further 5-10 mins.)
Allow the cookies to cool on the trays briefly, then lift onto to a cooling rack. Will keep in an airtight container, separated with baking parchment, for up to 1 week.