Line of Duty fans are convinced Dot Cottan revealed a major clue about H as he died Credit: Handout. His clue has lead Kate, Steve Arnott and Ted Hastings on the hunt for H ever since, with the ...

Felix Lazebnik, professor of mathematical sciences at the University of Delaware and an internationally known expert in graph theory, says this area of study has become the common language for ...

Dot, dot, dot, dot.” Hastings looked as if he’d been slapped sideways with a prize-winning halibut. “The letter H in Morse code is four dots,” elaborated DS Steve Arnott.