Dark Skies (1996-1997)	Series set in the sixties about a couple investigating alien appearences on Earth. Stars Megan Ward and Eric Close.
Doctor Who (1963-?)	The old but trusty BBC series about a time travellor who basically went anywhere and did anything. It's current status is uncertain, after it has been declared officially dead and officially not dead several times each.
Doomwatch	Entertaining BBC TV series about a group of scientist protecting the environment against all sorts of stuff.