The trailer for the highly anticipated sixth season of Line of Duty has dropped ahead of its release later this month.

The hit BBC show will make a return to BBC One on March 21 with a seven-part season, making it the longest series to date.

News of the its return has left fan wondering what could be in story for AD-12 in the show’s latest instalment.

Until now, details of the upcoming season have been kept under wraps.

The new trailer was posted on social media by the official Line of Duty Twitter account with a caption that said: Fellas, try to contain yourselves…”

Stars of the show Vicky McClure, Adrian Dunbar and Martin Compston all return as the one of TV’s favourite trios, Inspector Kate Fleming, Superintendent Ted Hastings and Detective Sergeant Steve Arnott.

Shalom Brune-Franklin will feature in the new season as AC-12’s latest edition, DC Chloe Bishop.

The guest lead will be played by Kelly Macdonald, who has starred in Trainspotting, Nanny McPhee and Harry Potter and the Deathly Hollows Part 2.

She will play Detective Chief Inspector Joanne Davidson, the senior investigating officer of an unsolved murder case who comes to the attention of the AC-12 team due to suspicios conduct.

In the trailer Kelly Macdonald’s character can be heard saying: "Whoever did it's got away with it.," speaking of a new murder case.

Superintendent Hastings can be heard telling his team of the force's 'highest profile investigation', later adding: "It will be our job to detect whether police corruption has contributed to this murder remaining unsolved."

Watch the trailer here:

When it emerged the new series will be seven episodes last month, Line Of Duty creator Jed Mercurio joked it looks like “AC-12 are losing their touch” as it was announced the series will have an extra episode when it returns to screens.

Filming of the sixth series of the hit police thriller began last year, however it had to be paused because of disruption caused by the coronavirus pandemic.

Line Of Duty began on the BBC in 2012.