Meet the modern day Captain Ahab, who is in prison for trying to save whales instead of killing them

This week, an appeals court in the Danish territory of Greenland upheld a previous ruling that Mr Watson will remain in custody until September while he awaits a decision on his possible extradition to Japan.

Watson, 73, was arrested in July in the Greenland capital Nuuk on the basis of an Interpol arrest warrant issued in 2012. He is accused of damaging a Japanese whaling ship and injuring its crew in an incident in the Southern Ocean in 2010.

Japan claims the crew member's injury was caused by a stink bomb used to deter the whalers. Watson's conservation foundation says its activism is based on “aggressive non-violence and intervention” to combat “illegal operations to exploit marine life.”

The foundation posted video footage of the arrest in Greenland online, showing Watson being handcuffed by police and loaded into a van. They warned that he could spend “the rest of his life in prison” in Japan if the extradition request is granted.

Speaking to The Telegraph, Omar Todd, co-founder of the Captain Paul Watson Foundation, said he feared Japan was trying to “silence” Watson’s campaign to protect whales and other marine life.

He said: “Paul has long been a thorn in the side of the Japanese government due to his tireless efforts to combat illegal whaling and other environmentally damaging practices. His activism has attracted considerable attention over the years and made him a target for those seeking to silence him.