Sir Michael Gambon will star alongside Helen McCrory in ITV's new legal drama Fearless, written by Homeland's executive producer Patrick Harbinson.
The acting veteran, 75, was announced as one of the stars appearing in the six-part series as filming gets under way, although details of his role have not yet been revealed.
Also joining the cast is actor and comedian John Bishop and Emmy nominee Robin Weigert, who is best known for appearing in TV series Deadwood, and Marvel's Jessica Jones.
Peaky Blinders' actress Helen was previously confirmed as the leading star.
She is set to take on the role of Emma Banville, a defence solicitor investigating the killing of a schoolgirl in East Anglia.
Emma is convinced a man has been wrongly imprisoned for the girl's murder and works against the police and intelligence services, despite powerful forces trying to stop her learning the truth.
Fearless has been described as a "crash zone where law and politics collide" by Patrick, who worked with McCrory's husband Damian Lewis on US drama series Homeland.
The series will be produced by The Disappearance Of Alice Creed's Adrian Sturges, and executive produced by Damien Timmer, managing director of the production company behind the programme, Mammoth Screen.
Timmer said of the latest casting news: "Michael Gambon is a legend, one of the UK's finest actors, and it's a real thrill for us that he will be joining the brilliant Helen McCrory in Fearless.
"The range and depth of the cast that director Pete Travis has assembled is testament to Patrick Harbinson's wonderful scripts, following Emma Banville as she risks everything in her quest for the truth."
Sir Michael, who has won four TV Baftas, is known for his extensive back catalogue of work across TV, film, radio and theatre over a career spanning five decades.
In recent years he has played Albus Dumbledore in six of the eight Harry Potter films.
He is also known for playing French detective Jules Maigret in ITV series Maigret, and for starring in BBC series The Singing Detective.
Other cast members confirmed for Fearless include Jonathan Forbes (Catastrophe), Wunmi Mosaku (Moses Jones), Jamie Bamber (Battlestar Galactica), Christine Bottomley (In the Club), Rebecca Callard (Ordinary Lies), Emma Hamilton (Mr Selfridge) and Rick Warden (Happy Valley).