First Night: Parade’s End, BBC2

"The thinking person's Downton Abbey" was the tag that had attached itself to BBC2's Parade's End, which is unfair since Sir Tom Stoppard began adapting the quartet of Ford Madox Ford novels long before the world had heard of the Crawley household and their servants – unfair but understandable, since both dramas follow upper-class Edwardian society into the trauma of the First World War and beyond.

But whereas Julian Fellowes created his drama from scratch, Stoppard (writing his first BBC screenplay in more than 30 years) had the knotty task of making televisual sense of one of the key works – alongside Ulysses and The Wasteland – of Modernist literature.

Stoppard began by de-kinking the novel's highly experimental chronology, which, in the original, zips about like a bat on Benzedrine.

Last night's introductory episode threw us head-first into the troubled marriage of Christopher Tietjens (Benedict Cumberbatch), a government statistician, and his flippant and adulterous wife Sylvia (Rebecca Hall) – a "Papist bitch" according to Tietjens's male supporter at his shotgun wedding in Paris – who has trapped him by becoming pregnant, probably with another man's baby. That Stoppard managed to launch this couple at all is a triumph in itself, for they were not the easily recognisable types that usually inhabit TV drama.

Tietjens, the self-proclaimed "last Tory", whose world, according to Sylvia, "ended long ago … in the 18th century", is not easy to warm to, and you can understand why Stoppard wooed Cumberbatch so assiduously. Perhaps no other actor of his generation is quite so capable of suggesting the tumult beneath a crusty, seemingly inert surface. Rebecca Hall was equally good, keeping her performance the right side of camp-vamp, while bringing the most out of such lines as "He's making corrections in the Encyclopaedia Britannica. If I killed him no jury would convict".

There was a peachy scene where Sylvia dumped one of her lovers (a louche drone called Potty), calmly expressing the wish that he doesn't "behave badly" as Potty raises a loaded revolver to the back of her head.

In fact Sylvia and Christopher's marriage is not quite the loveless sham it first appears to be – there is a need to torment each other, which suggests a certain ill-starred passion. The arrival, on a golf course, waving a "votes for women" placard, of the bobbed and gamine Valentine (Australian actress Adelaide Clemens), provided the third side of what will become the love triangle at the heart of Parade's End.

There are so many details to savour in this dense and ambitious BBC/HBO co-production that it will almost certainly reward multiple viewings. I only noticed one small – what you might call Downton – moment, and there probably wasn't much they could do about that: a vista of the British countryside that Tietjens loves so much, bearing the imprints of large-scale modern agriculture. On the whole, though, this was impeccable stuff. Pedants watching to nit-pick about historical verisimilitude will only be depriving themselves of something rare and rather wonderful.