We're right on the cusp of a brand new age for Doctor Who. The upcoming season 11 will see Jodie Whittaker steer the TARDIS in a fresh direction as the Thirteenth Doctor, alongside her squad of companions Ryan, Yaz and Graham (Tosin Cole, Mandip Gill and Bradley Walsh, respectively). New showrunner Chris Chibnall has been keen to emphasise that this is basically the 2005 reboot all over again and is hoping to wipe the slate clean. Even the Daleks supposedly won't appear.
While this is good news, it does mean that many of those questions we had by the end of Steven Moffat's lengthy era on the show, as well as those leftover from the Russell T. Davies years, will never be answered. Both previous showrunners introduced some major concepts during their tenures on the series - but they both can also be accused of dropping the ball sometimes when it came to wrapping the narrative up.
So, just before we venture into the era of the Thirteenth Doctor, let's first spend a moment looking behind us as we remember some of those perplexing Doctor Who plots that apparently got lost in time.