Heat oven to 180C/160C fan/gas 4 and line 2 baking trays with baking parchment. Pour 50ml/2fl oz boiling water over the raisins and leave to soak for 20 mins until plump. Drain, reserving the liquid.
Meanwhile, in a large bowl, mix together the oil and sugar. Gradually beat in the egg, along with the reserved water from the raisins, the cinnamon and vanilla extract. Sift the flour, bicarbonate of soda and a pinch of salt into the bowl, then add the oats. Finally, mix in the raisins.
Drop heaped tbsps of the cookie dough onto the baking trays, well spaced apart as they will spread when cooking. Bake for 12-15 mins until golden. Leave to cool on the trays for 10 mins before tucking in, or transfer to a cooling rack to cool completely. Will keep in an airtight container for up to 3 days.