In 1845, Sir John Franklin sailed from England with 129 men and two of the Royal Navy's finest ships, HMS Erebus and HMS Terror, to chart the last unmapped stretch of the Northwest Passage. They were expected back within three years. They were never seen again.

What followed became one of the greatest mysteries in the history of exploration. Scattered bones on a frozen island. Inuit testimony of starvation and cannibalism. A hastily scrawled note in the margins of an Admiralty form. And a Victorian public that refused to believe its heroes could have met such an end.

Russell Potter, one of the world's foremost Franklin scholars, joins Hugh to unpick nearly 180 years of searching, speculation, and discovery. He explains what we actually know, what we can only guess at, and why the mystery endures. Both ships have now been found, one r ...