Board Thread:The Panopticon/@comment-2249686-20200330214018/@comment-6032121-20200331114242

Ah, but you see, while you think multi-parters are defined from a production standpoint, that's only your opinion. And that is really the clincher. Some people think multi-parters are defined by narrative ties, others by hard-and-gritty production facts, and yet others by whether the BBC called them multi-parters.

True, there is debate on some Hartnell-era stories (another big one is The Dead Planet vs. The Daleks), but there are at least commonly-used collective titles that can be found on official sources such as VHS/DVD/Blu-ray releases, so it's not hard to pick one of those and stick with it. Whereas there isn't any kind of received wisdom on what to call NuWho two-parters, save possibly the Angels two-parter of Series 5 being popularly known as The Crash of the Byzantium.