Why it took them months, AND MONTHS, to let us know what we all knew already I'll never know. Although nice touch at the end with the phones, where they thought they'd make us think it was Max she was having an affair with (Kat thought she'd ring Max's phone to get him to warn Derek that Alfie knew it was a Branning. We could go into more detail as to how he arrived at that conclusion, but really it just involved lots of Neo off The Matrix type striding around the square, a bit of paper with 'Branning' on it, and a lot of shaaaaahtiiiin' ) - when we knew it couldn't possibly be, given Tanya gets re-hitched to her hubby on the 25th.
Then again, Tanya managed to bury him in the woods and he took her back, so stranger things have happened.
SPOILER ALERT: Derek winds up dead on Christmas Day, so I guess we can now add Alfie to the 'whodunit' list. You know, whenever you get the image of Derek and Noel Fielding in drag going at it in their rose petal strewn shag pad *heaves*. Apologies.