The 'accidental' severing of undersea cables or pipelines seem an almost daily occurrence these days but how reliant are we on this infrastructure, how much of it is there, and what steps are being taken to protect it? Business and economics editor Douglas Fraser investigates who might be behind these thinly veiled acts of sabotage and what their motivation might be. With much of the activity happening in the North and Baltic seas Douglas travels to Norway to see how the Navy there have long anticipated this risk and have partnered with the oil and gas industry to create a 'total defence' concept that extends deep beneath the waves.