The new series, titled The Gold, is based on the true story of the iconic Brink's-Mat robbery, dramatising one of the most remarkable events in British Criminal history.
WATCH: Are you looking forward to the new Downton Abbey film?
The two actors, who played Robert Crawley and Viscount Gillingham in the popular period piece, join a star-studded cast that includes Slow Horses' Jack Lowden, Mamma Mia's Dominic Cooper, Sanditon's Charlotte Spencer and Guilt's Emun Elliott.
Mission: Impossible star Sean Harris, Midsommar's Ellora Torchia and The Last Kingdom's Stefanie Martini also feature in the new drama.
The series is inspired by extensive research into the UK's 'crime of the Century' which saw six armed men break into the Brink's-Mat security depot near London's Heathrow Airport in 1983 and unintentionally stumble across gold bullion worth £26m.
Hugh Bonneville is due to star in a new BBC drama
Describing the impact of the robbery, the BBC writes: "The disposal of the bullion caused the birth of large-scale international money laundering, provided the dirty money that helped fuel the London Docklands property boom, united blue and white-collar criminals and left controversy and murder in its wake."
The drama is written by Neil Forsyth, whose previous credits include Guilt, Eric and Ernie & Me, and is directed by Oscar-winning Aneil Karia (The Long Goodbye) along with Lawrence Gough (The Last Bus, Snatch, Misfits).
Tom Cullen will join his fellow Downton star Hugh Bonneville in the new drama
While a release date for the new series is yet to come, we can reveal that filming for the new show began recently.
Speaking about the new project, the BBC's Commissioning Editor, Tommy Bulfin, said: "The fact that we have assembled such a talented and exciting ensemble cast is testament to Neil’s incisive interrogation of one of the most infamous robberies in British history and the remarkable events which came in its wake.
"And to have the brilliant Aneil Karia join fresh from his Oscar win is the icing on the cake. The BBC One audience are in for a real treat when this hits the screen."
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