Bodyguard was a ratings smash in Britain recently - the most watched drama there since the stiff-upper-lip crowd-pleaser Downton Abbey (2010 to 2015).

And for the first half of this six-part series, you see what the fuss was about. The slickly shot opener is simple but effective and edge-of-your-seat good. A vigilant off-duty police officer named David Budd (Richard Madden) foils a suicide bombing on a London-bound train as his two children sleep in the next carriage.

For his heroism, he is appointed the bodyguard for Home Secretary Julia Montague (Keeley Hawes), the powerful minister in charge of internal affairs.

But the troubled war veteran has post-traumatic stress disorder from his tour in Afghanistan and, when he realises Julia consistently voted to send soldiers over there, he begins to daydream about hurting her.

He is not the only one - as terrorist threats mount, she is pushing for a new law that will erode privacy and empower the security services. And her naked ambition to become prime minister is making members of her party and other officials nervous, triggering a series of Machiavellian moves to thwart her.

When an attempt is made on her life, it is David who comes to the rescue and the friction between the pair turns into sexual tension and more.

The first three episodes skilfully juggle this blossoming relationship and the action-thriller elements.

Madden imbues his square-jawed action hero with emotional vulnerability and boyish petulance, while Hawes delivers a more restrained performance as a manipulative politician who nonetheless seems to have some moral conviction and compassion.

The early exchanges between them and other key players are tightly scripted yet eloquent and the edgy camera work - plenty of paranoia-inducing close-ups and tight angles - builds up a general sense of paranoia.

But after a fantastic twist mid-series, this well-paced drama goes off the rails a bit.

Forensically, the various investigations by David and other officials trying to figure out who is behind the attacks do not quite add up. You will wonder why they do not work some things out much sooner.

The series becomes altogether more pedestrian halfway through, morphing into your garden-variety conspiracy thriller.

And the denouement is far too wordy and protracted, albeit peppered with some genuinely nail-biting moments. The show has earned your patience by this point, though, so you will gladly watch to the end.

Meanwhile, a new take on the Sabrina The Teenage Witch comic books, Chilling Adventures Of Sabrina casts Kiernan Shipka as the titular adolescent spell-weaver.

Half-witch and half-mortal, she is about to turn 16 and, on her birthday, will have to choose between the witching and the human worlds.

Set in the 1960s, the series is much darker than the fluffy popcorn version of Sabrina (1996 to 2003) starring Melissa Joan Hart. The horror elements and scare factor here are much stronger, albeit a little formulaic.

Yet the unevenly plotted show is rescued by a certain campy exuberance, especially in the scenes with Sabrina's two entertainingly witchy aunts, played by Lord Of The Rings star Miranda Otto and the grossly underrated Lucy Davis from Wonder Woman (2017).

Shipka, who was Don Draper's daughter on Mad Men (2007 to 2015), seems made for this kind of retro setting, both the actress and the era inflecting the character with an ahead-of-her-time intelligence and savvy.

The female-centric narrative also drags this franchise into the present day. For some, it will be hard not to watch this and think about the historical persecution of witches, how that was about misogyny and fear of powerful women - and how that continues in many forms today.