Anna Maxwell Martin has joined the cast of "Line of Duty".
The "Bleak House" actress is "dead chuffed" to have been asked to play
anti-corruption officer Detective Chief Superintendent Patricia Carmichael in the final two episodes of series five.
She said: "I've been a fan of Line Of Duty for years, so was dead chuffed to be part of series five. I'm so pleased I no longer have to keep it a secret!
"I feel honoured to follow in the footsteps of the host of great actors who make up the "Line Of Duty" family, and Jed Mercurio - of course - has written a brilliant character in Carmichael.
"She's a woman on a mission."
Showrunner Jed Mercurio is "delighted and flattered" to have the award-winning star on board.
He said: "I'm delighted and flattered an actor of Anna Maxwell Martin's status agreed to play this pivotal role in Line Of Duty.
"Anna was a pleasure to work with and brought real depth to the character of DCS Carmichael."
And bosses at World Productions, who make the crime drama, are "thrilled" to have landed the 41-year-old actress for such a key role.
Simon Heath, executive producer for World Productions, said: "We're thrilled to be working with Anna again, but in a very different role.
"I can't wait for the "Line Of Duty" audience to see what she's brought to the show."
It was recently revealed the series finale will be a huge 90 minutes long.
A source said: "Creating a closing episode which is the same length as some feature films shows just how huge this show has become and how much the corporation values it.
"Jed also felt it was necessary to create a bumper finale to tie up the many loose ends created in this series twisting storylines."