Eagle-eyed Line Of Duty fans have been well and truly spoilt when it comes to subtle messages and Easter eggs hidden in plain sight in the latest series of the BBC police drama.

Sunday night’s episode was no exception, with viewers picking up on what appeared to be a reference to one of the show’s biggest ongoing storylines hidden in some graffiti.

In one scene, Kate Fleming and Ted Hastings returned to a heavily-graffitied underpass to have one of their shady private meetings, and fans (including The Chase favourite Jenny Ryan) couldn’t help but notice a stonking big “H” written on the wall in spray paint.

Others also pointed out that the word next to it appeared to spell out “not”, with some suggesting it could be a clue, while others wrote it off as a red herring – but a fun one all the same.

The mystery about the identity of “H” was somewhat resolved at the end of series five, when it was revealed that “H” was actually a code name referring to one or a group of senior ranking corrupt police officers within the Central Police.

It was also revealed that there are four people pertaining to be “H”, the last of which remains unknown.

Last week, fans noticed another hidden “H” in the tiles in the background of John Corbett’s widow Steph’s kitchen.

Admitting that sometimes details like this were deliberately used as misdirection, Line Of Duty creator Jed Mercurio previously told Radio Times: “If you have created a set of mysteries, you also have to understand the significance of misdirection and red herrings.”

“We do use misdirection at times,” he added. “And it’s deliberate.”

Line Of Duty continues at 9pm on Sunday night.