This image taken in August 2007 from Calshot Spit in the Solent shows the Admiralty Tug Sheepdog (A250) towing the Admiralty Lifting Barge 1236A up Southampton Water, presumably heading for the Marchwood Military port in Southampton. Sheepdog was built in 1969 with a gross tonnage of 151 Tons and I believe (from Internet sources) was based then at the Naval dockyard at Portsmouth.