Board Thread:The Reference Desk/@comment-90.202.235.30-20150819012613/@comment-1398253-20150910145337

Besides, killing her off would've created more unanswered questions, notably, the fates of Sky Smith (who was still at school), Mr Smith (alien technology, but pretty much unmovable), and 13 Bannerman Road (there's so much alien stuff there I suspect UNIT would confiscate it all and stick it in the Black Archive). At least we know K9 is with Luke.