There's a horrible accident with a vortex manipulator and Jack Harkness or River Song (or somehow, both of them together), end up going very, very far back into the past indeed, and wind up somewhere, sometime, in Middle-earth.
Can Jack bed at least one member of every sentient race? Those Ents might be a problem, but I'm sure he'll find a way.
Can River Song put Sauron's eye out with her blaster? ("You are an associate of the Doctor's, you will show mercy." "I'm River Song, check your records again!" "MERCY!")
Most importantly, who winds up with the Silmarils, or the Arkenstone, or the Ring? And when the Doctor arrives to rescue him/her/them at last, how much does he scold them for stealing them/it?
Jack Harkness and/or River Song fall into Middle-earth
Can Jack bed at least one member of every sentient race? Those Ents might be a problem, but I'm sure he'll find a way.
Can River Song put Sauron's eye out with her blaster? ("You are an associate of the Doctor's, you will show mercy." "I'm River Song, check your records again!" "MERCY!")
Most importantly, who winds up with the Silmarils, or the Arkenstone, or the Ring? And when the Doctor arrives to rescue him/her/them at last, how much does he scold them for stealing them/it?