It is "off the scale" in terms of quality and a match for his favourite dramas The Wire and Mad Men, according to George Entwistle, the BBC's new director general. And Parade's End, Tom Stoppard's adaptation of Ford Maddox Ford's tetralogy that comes to a close on Friday, has been unashamedly literary. Defiantly highbrow, with luxuriant production values spilling from its starched fly collars, this is a drama that has class stamped right through it. (In more ways that one).

Starring Benedict Cumberbatch and Rebecca Hall as Sylvia and Christopher Tietjens, BBC2's five-part adaptation has apparently moved Andrew Davies, the so-called king of costume drama, to read the novels that Parade's End is based on. And it's threatening to have much the same effect on me.

With a plot focusing on an Anglican Tory civil servant, who is a leading figure in the Department of Imperial Statistics, it perhaps doesn't sound like the most compelling of stories. But Cumberbatch's portrayal of Tietjens fighting a one-man battle with the evils of modernity as he perceives them – permissiveness, dishonesty and errors in the Encyclopedia Britannica, which he enjoys correcting over breakfast – has made Friday nights into even more of a longed-for destination.

Cumberbatch manages to be both awkward and self-assured, vulnerable and yet totally oblivious to the world around him in a way that seems not only striking but also convincing (an important attribute, given the fact that some of his character's behaviour belongs to not just another age but another planet).

Through the curl of his rubbery-looking mouth, Cumberbatch communicates Tietjens' decision to apparently not only defy the modern world but act as though it doesn't exist and never will. "I stand for monogamy and chastity," he declares. "And for not talking about it." There is something deeply moving in all this, as well as oddly comic – and we can well understand the rage this prompts in his flighty, cruel, passionate wife. There is smugness as well as virtue to Tietjens, but even early in the series he reveals an awareness that he is the last of his generation or parade to be like this.

This old-fashioned moralist finds his principles severely tested, however, by Sylvia – played with wit, sass and elan by Hall – who decides to "run orf" with the dim-witted Potty Perowne. And he, rather against his better judgment, falls for the spirited suffragette Valentine Wannop – or, as Sylvia calls her in this Friday's episode, "that scrub-faced ladies champion of the regular bowel movement".

There are many such delicious moments in a show that, under Susanna White's direction, is a visual feast. I particularly loved Tietjens and Valentine on the horse and trap in episode one – a beautiful, simple white mist evoking a timelessness and captivating purity. Also striking are the kaleidescope motifs of the opening credits, which have slipped cleverly into the drama itself – thereby helping to evoke the vastness and complexity of they story's social canvas.

An array of fabulous supporting characters have also been excellent viewing, often cast as wild eccentrics – among them Rufus Sewell's mad, filthy, sweary cleric, Rev Duchemin, who I particularly enjoyed watching. Roger Allam's baffled general Campion, with his sheer, plummy astonishment at the way Tietjens conducts his private life, has also made me laugh every time.

Parade's End looks beautiful, is wonderfully made and has some fantastically resonant and descriptive language: Tietjen's comparison of the noise on the Western Front to a "wet canvas being shaken out by a giant" just one of many sublime moments of dialogue. I've also enjoyed getting to know a source text that is not, perhaps, as well known as others.

There are, however, some caveats. Some of the structure has been a little patchy – the worst example being in episode four, when nothing really developed, except for Tietjens getting into a frightful flap (as he might describe it) over his job securing supplies for the troops fighting at the front. And I do wonder whether this drama would have received the same reception if it hadn't been written by Stoppard. He has admitted – perhaps tellingly – that he watches little television. And at times, his pacing and structure have been off-beam.

There's also the question of whether we're fast approaching saturation point when it comes to early 20th-century drama, what with Downton Abbey, Birdsong, Titanic and the upcoming Mr Selfridge on ITV1. "I'm sick of this posh porn" one rival drama producer told me the other day. And for some, that might well have been a contributing factor to whether they stuck with the drama.

But possibly not as much as the scheduling – which has been decidedly odd. Why launch such a flagship drama in the middle of August on a Friday night? Some inside the BBC suggest that, while Entwistle was yesterday lauding the show, bosses didn't have total faith in what is patently a strong autumn Sunday-night drama.

Personally, I've found it hugely watchable, all things considered, and can't wait for Friday's closing episode. What about you?