Complex sentence: During the war Barrow Hill at Southwell had been used as a camp, and the admiralty decided that the cliff-top location would make an ideal base for a new establishment to work alongside the naval base and HMS Osprey.
Split into simpler sentences: During the war Barrow Hill at Southwell had been used as a camp, and as such the Admiralty saw the site's potential. The decision was made to turn the hill into a base for a new establishment to work alongside the naval base and HMS Osprey.