Firth will portray Swire, who tragically lost his daughter Flora in the event, and has pursued justice with his wife ever since.
David Harrower (Blackbird) is the lead writer, alongside Maryam Hamidi (Vigil) as a guest writer.
Otto Bathurst (Peaky Blinders) is lead director, while Jim Loach (Save Me) will also direct an episode.
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The show will have five episodes in total.
In December 1988, 259 passengers and crew were killed when Pan Am Flight 103 exploded over Lockerbie 38 minutes after take-off. Eleven residents lost their lives as the plane came down over the Scottish town.
In the wake of the devastating event and Flora's death, Swire became the nominated spokesperson for the UK victims' families, who want truth and justice.
As explored in the series, Swire embarks on a "relentless journey that not only jeopardises his stability, family and life, but completely overturns his trust in the justice system".
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The show is based on the book The Lockerbie Bombing: A Father's Search for Justice by Jim Swire and Peter Biddulph.
Further casting is yet to be announced, with filming set to commence in early 2024.
Lockerbie will be available on Sky and NOW in the UK, Ireland, Italy, Germany, Switzerland and Austria, and on Peacock in the US.
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