This article first appeared in Radio Times magazine.In a hazy police station atrium in south Wales, police consultant John Chapel and DI Janie Mallowan are confronting a murder suspect. Their evidence? Impeccable. Their psychological profiling? Absolutely top-notch. Surely, they’ll get this “whodunnit” wrapped up in no time.Except – CUT! – there needs to be another take. As Death Valley stars Timothy Spall and Gwyneth Keyworth wait, a smoke mach…