It's the question that has been bugging Line of Duty fans for what seems like forever and even more now so after Sunday night's cliffhanger episode, so who is H?
Whilst diehard fans search previous episodes for hidden clues, others have turned to their home devices to see if they can shed any light on the elusive H.
Some fans have decided since their Amazon Alexa device seems to know everything, she might know who H is?
So what happens when you ask 'Alexa, who is H?'
Well she gives quite a funny answer, going full blown Ted Hastings with her reply.
She says: "Mother of God! I can't tell you that, those bent coppers will have me bumped off!"
Fans are eagerly awaiting the next episode of the hugely successful BBC series which was filmed in Belfast.
Earlier today the BBC confirmed the return of Bafta award-winner Anna Maxwell Martin as Detective Chief Superintendent Patricia Carmichael.
Viewers will remember no-nonsense DCS Carmichael from series five, where she was brought in as an independent investigator from AC-3 after suspicions mounted over the integrity of Superintendent Ted Hastings.
Speaking about her character's return, Anna said: "Pat’s back, I can’t remember what she’s doing there, nor would I be allowed to blab, but suffice to say she’s got some new clobber and she’s ready to bust some balls."
Fans can see her in action when the latest episode airs on Sunday, April 18th at 9pm on BBC One.
