In reply to Alex Purser:
Definitely Loch Coruisk on Skye, the most moody, lonely, brooding and unspoiled place in the British Islands. Some amazing geology where the river takes a short trip out of the loch, over flat glacial slabs and pours straight into the sea. Take the boat from Elgol ad stay the night at Camasunary bothy in the next bay then walk out.