Plot: Matt Baker and Ellie Harrison visit the largest privately owned estate in Devon, which has been in the same family for more than 700 years, to discover how the 25,000 acres are shaping up to the future.   Matt joins the calving team at Clinton Devon Estates and sets the wheels in motion at a 900-year-old watermill, while Ellie checks out a mammoth project where the sea will be more than welcome to flood the land