The article says -
'The ITV series, using a screenplay by Kris Mrksa, who wrote the spooky BBC1 Requiem series, is based, in part, on a published investigation of the murders by author Carol Ann Lee.'
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I hope the researchers also use lots of other sources. There is a lot online, on youtube & in other books. Crime drama's often have long scenes of police interviews. If they quote from the online Bamber police interviews, that would be very damaging for him.