Three-sided football: A game of alliance and betrayal
23 January 2014 Last updated at 23:43 GMT
It seems like a typical Sunday afternoon game of football, but there's a big difference - there are three teams on the pitch.
Deptford 3S Football Club is playing Philosophy Football FC and Strategic Optimists FC, at the same time.
This is the complex and curious game of three-sided football, an invention of Danish Situationist philosopher and artist Asger Jorn.
Played on a hexagonal pitch, the rules are similar to normal football, but it is the team that concedes the fewest goals, rather than scores the most, that wins.
This leads to all sorts of tactical subtleties, as BBC News discovered at a match in New Cross in London.
Video journalists: Dan Curtis and Tom Beal.
Asger Jorn Photo by G Jespersen/Getty Images.
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