With the customary police escort, a visiting submarine heads towards HM Naval Base at Faslane. UPPLAND is one of three submarines built in the 1990s by Kockums for the Swedish Navy, and she was commissioned in 1997. She is powered by an Air Independent Propulsion System, which comprises auxiliary Stirling engines that use liquid oxygen and diesel fuel to power 75 kilowatt generators, either for propulsion or to charge batteries. This allows an underwater capability of around two weeks at five knots. For surface use, two diesel engines are also fitted. UPPLAND was visiting the Clyde to exercise with the Swedish ship BELOS, seen arriving a few days before.