That story about Joaquin Phoenix – did he or did he not go mad? – is still bubbling away. As you may recall, about a year ago the actor suddenly decided to grow a beard and begin mumbling like a maniac during interviews. Then he claimed he was changing careers to become a (really bad, as it transpired) rapper.

All the while, Casey Affleck, actor and brother to Ben, filmed his friend for some sort of documentary. It was generally assumed that the film was part of a massive, clever-clever hoax – a class of post-modern art experiment.

The movie, I'm Still Here: The Lost Year of Joaquin Phoenix, is now finished, and Affleck the Younger has begun shopping it around producers. But here's the thing. Casey swears that it is not a hoax. Phoenix's change of career was, he claims, sincerely intended, and the film is a serious record of that experiment.

The budding director, who is married to Phoenix’s sister, explained himself thus:

“He said he didnt want to act any more, he wanted to try doing music, and that, right there, says something’s going to happen. I had no idea what exactly was going to happen and all that would unfold.”

It all sounds fascinating and, with all that talent attached, the film will surely find a buyer.