Hit BBC police drama Line of Duty left fans with the mother of all cliffhangers after the latest episode - with the question just who is dodgy Detective Jo Davidson related to?

Fans were left freeze-framing their TV when a photo file was presented to AC-12's boss Ted Hastings with evidence that someone on the police database was found to be a blood relative of Davidson.

But just who was in the file? It left Hastings uttering his signature line: "Mother of God" and fans guessing ahead of episode five on Sunday.

Here are the most likely contenders, and the fan theories behind the names.

Tommy Hunter

He was the leader of the Organised Crime Group (OCG) from right back in series one. And the fact that he was Scottish, and Jo is too, made fans make the obvious connection that they could be related. Could he be her father or brother?

One fan wrote on Twitter: "I have been thinking about this far too much, but my fave theory is that Jo is Tommy Hunter's daughter, and being blackmailed by the OCG to pay off his debts #lineofduty #LineofDuty6."

Jimmy Lakewell

Jimmy Lakewell in Line of Duty

Dodgy lawyer Jimmy Lakewell, from series four, reappeared in series six for explosive scenes as DS Steve Arnott tried to get him to agree to releasing his information on the OCG.

But after the failed ambush to kill him, Jimmy then refused to co-operate with AC-12 and swiftly met a murky end in prison. When Jo was told, her reaction has aroused suspicions that they could be brother and sister.

Fans think it adds up. One Twitter fan said: "Rewatched Line of Duty and I'm now kinda veering towards Jimmy Lakewell being Jo's relative after her reaction to Ryan telling her Jimmy had been killed."

Another agreed saying: "sounded to me like the match was not from serving Police officers database but another they hold. I think Jo is related to Jimmy Lakewell, Ryan made a point of telling Jo - maybe a double meaning??"

Terry Boyle

He's the man that the baddies seem to be trying to frame for the murder of journalist Gail Vella. And Terry has history of being used by the OCG for cover-ups - not least having his fridge used for years to hide the body of murdered Jackie Laverty.

What if Terry is actually Jo's brother? And trying to protect him from being killed by the OCG is how she's got so deeply embroiled in all of the drama?

Fans on Twitter reckon so with one saying: "I reckon Jo's mystery relative is Terry Boyle... they're both being used by the OCG so its possible that they're siblings without knowing it."

Ex-police chief Mike Dryden

Michael Dryden (Mark Bonnar)

The dastardly former deputy chief constable Mike Dryden (who was brought down by AC-12 in series two) has one big clue going in his favour - he's also Scottish like Jo.

The shamed cop, played by Mark Bonnar, would fit the age profile of the father of Jo.

And as yet we've only seen Jo rage at a photo that appears to be that of her and her mother in her strangely secure flat.

John Corbett

Stephen Graham played undercover cop John Corbett in Line Of Duty

Eagle-eyed viewers have spotted a big clue that Jo might well be related to John Corbett - the undercover cop who was killed in series five.

For they say that the picture in Jo's flat of what looks to be her mother has similarities to the police file photo of John's mother - who was Anne Marie-McGillis.

Mrs McGillis was a police informant in Northern Ireland who went missing in 1985. John was born in 1979, the same year as Jo, but was adopted aged six when his mother went missing and his father Anthony had been killed.

Anne Marie's remains were not found until 2001. She had been tortured and shot once in the head.

John was adopted by his aunt Sorcha Corbett and her husband Robert and went to live with them in Liverpool.

Meanwhile his widow Stephanie has featured in the latest series meeting separately with Hastings and Arnott - which has aroused suspicions of what exactly she is up to in all of this.