The unlikely YouTube hit of the moment is a 40-minute video about a little fishing boat. More than 1.5m people, mainly in Japan and China, have watched this ocean drama, only a tad fewer than those who logged on to a 40-second clip about Tyson the skateboarding dog.

The featured Chinese trawler is at the centre of a September incident that brought Sino-Japanese relations to their lowest point since 2005. The footage, leaked last week, purports to show a Chinese boat ramming a Japanese coastguard ship in waters close to uninhabited, but fiercely contested, islands known as Senkaku in Japan and Diaoyu in China. Its release has reignited controversy over Japan’s arrest of the captain, which set off a diplomatic shoving-match between Beijing and Tokyo. So intense was the political pressure from Beijing that Japanese prosecutors released the captain without pressing charges, citing concerns about Sino-Japanese ties.

The video appears to have been leaked in an effort to back Japan’s story: it had no option but to arrest the captain for deliberately colliding with a ship near the Japan-administered islands. Beijing has consistently denied the fishing boat acted provocatively, though many Chinese netizens have branded the captain a hero for precisely that.