Looks like one of these:http://en.wikipedia.org/wiki/Skjold-class_patrol_boat
KC advises me it's P965 Gnist, delivered in 2012 to the Royal Norwegian Navy. He goes on, "It's a Norwegian Skjold class patrol boat - reputedly the fastest armed boat in the world - hence the noise of the four gas turbines!"
Thanks too to Fuimus, who also identified it. Jon
I saw a lot of Dutch army vehicles on the A9 on Sunday afternoon so perhaps one of the joint NATO exercises is underway or about to be?
It's that time of year when the major military exercise takes place - this year - Joint Warrior 131 - starting 15th April