Copper's hunch

The Tenth Doctor playfully referred to Rose Tyler's deductions while analysing the scribble creature as a "copper's hunch". "Permission to follow it up, Sarge?" She had deduced that a girl who'd caught her attention on Dame Kelly Holmes Close had something to do with the creature, saying the scribble might have been a mistake drawn over by a child. They went to her house to investigate. (TV: Fear Her)