ladyonyx04 said
Actually I have a Fourth Doctor thing that was never released on TV because the BBC had a strike, and some that are completely lost to the archives. Don't know from which Doctor they are missing from...
Shada never aired on TV, but they did release it on VHS (and I think DVD as well) eventually. As a result, it's available online, as well, so it's not completely unwatchable.
The lost episodes are ones that BBC completely destroyed back in the 70's, back when archiving for these sorts of things wasn't as good and, without digital technology, all that film took up actual, physical storage space and so sometimes old things got thrown out to make room for new things. BBC was never able to release them on VHS or DVD afterwards and, since fan recordings of shows were extremely rare back then, I'm pretty sure hardly any of them were recovered. About a third of Hartnell's episodes and like half of Troughton's were lost in that way. Thankfully after that they cleaned up their act and stopped destroying old content. :/
However, it is clear that BBC is at least
attempting to make up for their past mistakes. Since the audio was still salvageable for all of them, they do make that available - in fact they even have narration covering everything that should've been conveyed visually, which pretty much turns the episodes into an audio drama, but that's still way better than nothing. Also, in the case of a few episodes, they created animated versions to replace the original video. ...The animation isn't very good, in my opinion, but at least it's an attempt. Also, BBC's website has a list of all the lost episodes with a note at the bottom saying something like "If you have any Doctor Who content that you think might be of interest to us, here's how you can contact us". So they are still trying to fill in those gaps in the episodes, it seems. But unfortunately I imagine VHS copies of episodes people had recorded at home ~45-50 years ago are rather hard to come by.
