Does this Ted Hastings speech from the first-ever Line of Duty episode give crucial information about his past in Ireland?

• Anna Maxwell Martin will guest star in a "pivotal" role in the final two episodes of Line of Duty series five
• Line of Duty series 5 recap: 8 major revelations in that EXTREMELY dramatic episode 4
• Who is John Corbett? Everything you need to know about Stephen Graham's character in Line of Duty

With this in mind, we rewound back to the first episode of series one and found this scrap of information, which could become massively significant...

Where was Ted Hastings during the Troubles?

Remember in the first-ever episode of Line of Duty, back in 2012, when a sulky DS Steve Arnott (Martin Compston) accused Superintendent Ted Hastings (Adrian Dunbar) of the "victimisation of a black officer?" Steve objected to the scrutiny of DCI Tony Gates (Lennie James), and Irish Catholic Hastings did not take well to this line of questioning from his new AC-12 recruit.

"Hang on a second," a furious Hastings told Steve. "Don't you talk to me about victimisation. What are you saying? Let me tell you something, son.

"Me and my best mate, we went through basic training together, okay? First year out they sent us on this particular job, the two Catholics – are you with me? We go straight over a pipe bomb. I end up in intensive care, him they bury. The log book goes missing, nobody says a word. Don't you talk to me about victimisation."

Treading on slippery territory, he then added: "Nobody's blacker than me, son."

Hastings was once a member of the Royal Ulster Constabulary, and according to his own account, he and his best friend were deliberately sent into the path of a pipe bomb planted by a loyalist paramilitary group; the unit colluded in a cover up.

At the time, this didn't seem wildly significant, except to demonstrate the personal experiences which may have fuelled Hastings' crusade against "bent coppers", but now we're wondering if creator Jed Mercurio planted the seed of series five right back in the very first episode of Line of Duty.

Is there a connection between Ted Hastings and John Corbett?

We now know that John Corbett was actually born "John McGillis" in Belfast, but was adopted and given a new name in 1989, when he was ten years old.

His father Anthony Patrick McGillis died in 1984; his mother Anne-Marie McGillis passed away in 1989. And in the same year he was orphaned, he moved from Belfast to Liverpool to live with adoptive parents who were most likely close relatives of his biological parents.

By the end of series five episode four, we still don't know how his parents died, but this would have been during the Troubles – and it was also during the time Ted Hastings was most likely serving in the Royal Ulster Constabulary. At this point, we have to wonder if Hastings is connected with the death of Corbett's parents in some way.

Adding weight to this theory is Corbett's attack on Ted Hastings' wife, Roisin (Andrea Irvine), in which he inflicted paramilitary punishment wounds to her wrists, knees and ankles. "He said you’d know why he’d done it, he said you’d know what you’ve cost him," Mrs Hastings told her estranged husband from her hospital bed.

There's also the question of "Anne-Marie", with Corbett's wife fending off questions from Steve and DI Kate Fleming (Vicky McClure). "They was asking about Northern Ireland,” Steph Corbett (Amy De Bruhn) told her husband down the phone. “They was even asking about family over there.”

“Well did they know anything? Anything about my mum, and anything?” John responded, while Steph asks: “What’s this all about? Do they know about Anne-Marie?”

So at this point we're wondering...

THEORY 1: Was Ted Hastings' dead "best mate" actually Anthony Patrick McGillis, who died in 1984? Does Corbett believe that Hastings actually killed his father, or is responsible for his death? If so, is he right, or was Hastings falsely implicated in the cover-up from his unit?

THEORY 2: Did Hastings harm or torture Anne-Marie McGillis in 1989? Did he kill her? This could explain the torture of Roisin Hastings and Corbett's personal vendetta.

THEORY 3: There is no connection, this is all just a "Ted Herring" or a "Jed Herring", and Jed Mercurio is winding us all up. John Corbett (aka John McGillis) is referring to something else, and he and Hastings both just happen to be from Belfast, which – to be fair – has a population of more than 300,000.

Hopefully we'll get some answers soon...

Line of Duty continues on Sunday at 9pm on BBC1