The Union Flag was the flag of the United Kingdom.
Rose Tyler wore a shirt with the flag on while visiting wartime England. (DW: The Empty Child/The Doctor Dances) She later corrected Eddie Connolly's mistake of calling it the Union Jack; a title only applied while present at sea. Rose also corrected his positioning of the flag. (DW: The Idiot's Lantern)
In place of their recognition code, Ironside Daleks had the Union Flag. (DW: Victory of the Daleks)
