I'm one of those ancient types that still records Doctor Who episodes on tape and edits out the commercials while doing so. Anyway, while I agree that both Doctor Who
generally stand apart from one another, I did record the Torchwood: Children of Earth
series between two episodes of David Tennant's run, and while his Doctor was noticeably absent during CoE
(and a point was made of that), it was a fine case of Doctor Who
fitting seamlessly together and gives backstory to what Captain Jack was doing moping about that alien bar in Tennant's final episode, IMO.