Slice the courgettes in a food processor, using the fine disc, and pat dry on a clean tea towel. Toss the slices in a plastic bag with the flour, well seasoned. Heat the olive oil in a large frying pan with the rosemary, discarding the herb when the oli is hot, and add 1⁄4 of the courgettes. Fry the courgettes in batches on medium high heat for 2-3 minutes until light golden. Drain on kitchen paper, serve hot.