If ever a TV series was ripe for a Doctor Who-style modern makeover, then this is it. Sapphire and Steel was late-70s Britain's answer to The Twilight Zone, complete with creepy tinkling theme music and fantastically portentous introductory voiceover. And like The Twilight Zone, we were given stories of inter-dimensional slippage, time-shuffling wonkiness, and not entirely logical plot resolution.

But more than anything, Sapphire and Steel was just deeply disturbing: even now, some 30 years after first watching it, I can still remember the terror inspired by one S&S nasty, a faceless being that somehow exists only in old photographs. Having now seen it again, I can confirm that the episode is still extraordinary.

Back before Joanna Lumley had discovered her inner PR airhead on Absolutely Fabulous, she was quite a passable aristocratic ass-kicker. David McCallum, arguably a bigger star at the time after The Man from UNCLE, had perfected an intense, furrowed-brow glare. The idea, clearly, was that they would borrow their character from the substance they are named after: she is all delicate translucent beauty; he is hard as nails.

What would be almost unthinkable now, though, is the way the narratives are unspooled over several episodes, and are filled with elongated pauses, bizarre non-sequiturs and random story jumps. It suits the content, but it's so unlikely in a modern show, that it feels almost avant-garde. Take the very first scene of the very first episode, for example: it shows a kid doing his homework on the kitchen table, followed by about 50 shots of ticking clocks.

This show, it would seem, is about time. And despite the shoddy effects and threadbare production values – this is the glorious era of filming everything in the same quarry in the west London suburbs – series creator PJ Hammond summoned up a mood of creeping unease that gripped like a vice. Truly, one for the ages.