Fans were left less-than-impressed when Detective Sergeant Steve Arnott revealed he had noticed Dot Cottan tap out 'H' in Morse code during his dying declaration on Sunday's Line of Duty.

WARNING - CONTAINS SPOILERS: The Line of Duty finale has left viewers with the same question about who is H but there is a big clue in Dot Cottan's death throes ...

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 ...

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.

Line of Duty fans gripped by series 5 finale ... "It’s Morse code. Dot dot dot dot. ... “The letter H in Morse code is four dots. ‘H’ is not an initial, it’s a clue. Four dots.