User:SOTO/Forum Archive/The Panopticon/@comment-1293767-20151029072618/@comment-5918438-20160108023420

Now, if we had this discussion a year ago, I would have been okay with saying "writer and director" because it wouldn't have made any difference. This series, though, we got a new oddity. The two-parter written by two writers. That exists now. And if you say that Heaven Sent and Hell Bent are "clearly" intended to be a two-parter despite having almost nothing in common, then you cannot deny that The Girl Who Died and The Woman Who Lived were also intended to be a two-parter. Note, above, my list of series 9 titles. All two-parters, including TGWD/TWWL and HS/HB follow a very similar naming scheme, and the two true standalones in the series are the only ones which do not.

So, now at the start of 2016, "two-parter" no longer means that both parts are written by the same writer. That may be a common convention, but it is now no longer the case 100% of the time.