The Adventure of the Sinister Stranger

From BBC Doctor Who News:

"We're delighted to officially announce that Series Four of Doctor Who will commence with Partners In Crime at 6.20pm on Saturday 05 April 2008, BBC One."

That seems very early -- but remember when the series was on at that time anyway?  Also, turns out that first episode title is also an Agatha Christie title reference.  If she'd also written a novel called The Sontaran Stratagem it would look like a was pattern forming.