Vicky has played Kate Fleming, an anti-corruption officer frequently required to go undercover in the hit drama, currently in the middle of Series 4.
She told Graham Norton during her appearance on his chat show (to be screened tonight): “You can only be undercover so often, so if I am in Series 5 there will have to be some changes.”
There are two more episodes to go in the current series, which has seen the show move from BBC Two to BBC One, but Vicky resisted Graham’s request to spill any beans, including whether her character Kate makes it in one piece all the way to the final credits.
Writer Jed Mercurio is celebrated for killing off some of his lead characters when viewers least expect it, but Vicky told Graham: “I am definitely in next week’s episode. So much happens in the last two hours, it’s great.”
Vicky revealed that the show’s six episodes are filmed in two sets of three, which helps the actors learn their intensive interrogation scene dialogues for which the series is celebrated.
“I think filming all six in one go would be overwhelming as there is so much to learn - it would be ‘lines and lines of duty!’”
Series 4 stars the show’s regulars - Adrian Dunbar, Martin Compston alongside Vicky - with the series antagonist Thandie Newton. Last week’s episode saw Thandie’s DCI Roz Huntley turn the tables on AC-12, accusing its chief of sexism and fabricating evidence in pursuit of a conviction.
Vicky appears with fellow guests Rob Brydon, Harry Styles and Brendan O’Carroll on ‘The Graham Norton Show’ on BBC One at 10.35pm. ‘Line of Duty’ continues on BBC One at 9pm on Sunday.