Its description on iPlayer:
Novelist Naomi Alderman investigates the extraordinary sub-culture of internet fan fiction and asks how it is influencing the future of popular culture. ( More... )
My personal thoughts: I found it an amusing and sympathetic look at the phenomenon, though I thought a couple of the historical parallels a little strained. And, of course, there are as many ways of looking at fanfic as there are fanfic readers and writers, so I can't expect those interviewed to share my opinions on all points.
Those in the UK can find it on iPlayer for the next week: When Harry Potter Met Frodo: The Strange World of Fan Fiction
ETA: I see from Google that Alderman has form in the Whoniverse.