10 Doctor Who Episodes More Important Than You Realised

10. The Next Doctor

Building on the response to David Tennant's announcement that he was leaving Doctor Who, The Next Doctor was a tremendous bit of misdirection from Russell T Davies.

David Morrissey was not David Tennant's replacement, but was instead Jackson Lake, a man who believed he was the Doctor after an accident with an infostamp.

Which brings us to the importance of The Next Doctor in the history of Doctor Who. Because, while we'd seen sketches of previous incarnations in John Smith's journal of impossible things in Human Nature, we'd never seen any actual footage.

And so it was that, upon activating the infostamp, footage of the first eight classic Doctors (plus Eccleston and Tennant) appeared on TV on Christmas Day 2008. While we'd had it confirmed time and time again that NuWho was a continuation, it was thrilling to have the lineage displayed for all to see.

The Next Doctor was the last episode of Doctor Who to be filmed in standard-definition. From The Planet of the Dead onward, it was shot in HD, and now, years later, UHD.

To fit alongside the other 2009 specials, The Next Doctor was the first Doctor Who episode to be upscaled to high-definition, another feather in its cap of importance.