To The Death is a moderately satisfying end to the fourth season - taken on its own terms, rather good, though not quite as good as I was hoping for. (Then again, most Who finales leave me feeling that way.) It wraps up the story of the second Dalek invasion of Earth started in Lucie Miller, with much drama, death and destruction.
Further discussion requires SPOILERS.
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I'm not going to go on about this at great length because
Surely there is also a fairly major continuity problem? (Though sometimes problems are opportunities, I suppose.) In To The Death, the Doctor clearly remembers the events of Patient Zero; but my memory of Blue Forgotten Planet is that Charley zapped all the Sixth Doctor's memories of travelling with her. Or am I wrong on that point? Might go back and listen to that sequence again while waiting for next month's releases. Though I have the new Gallifrey series to get through first...