As proof of how much the BBC has upped the ante where post-Edwardian, end-of-empire costume dramas go, the man who has adapted Ford Madox Ford's Parade's End tetralogy – Sir Tom Stoppard, no less – admitted recently that the work had a "baffling structure".

He also said he got one of the five episodes "completely wrong". (It was number three, if you're interested, but he'll have it fixed by the week after next, I'm sure.)

Mind you, last night's opening episode on BBC Two wasn't exactly straightforward. Helpful subtitles occasionally said things like "Two months earlier" and added a semblance of direction to the non-linear narrative. But if you hadn't figured out by the 10-minute mark that several years had been telescoped into the choppy early action, you were in trouble, especially as new characters came at you in waves.

So Parade's End is no Downton Abbey, though it shares a few of that show's attributes. Like all good costume dramas, it features a love triangle (only glimpsed in episode one, but there's more to come). It also has a moral code we sneer at while at the same time feeling nostalgic for, women in wide-brimmed hats and horses. Lots of horses. These last were often to be seen being stroked and fussed over by Christopher Tietjens (Benedict Cumberbatch), youngest son of an aristocratic Yorkshire family whose stately pile he described to bob-haired suffragette Valentine Wannop (Adelaide Clemens) as being "older than Protestantism". Tietjens is something in government, a bright and prickly young man who, when he meets people, says things like: "You've written the only novel since the 18th century I've not had to correct in the margins." He's a bit like Sherlock Holmes, in other words – and in his brother, Mark Tietjens (Rupert Everett), he has a sort of Mycroft character too.

Tietjens falls for Valentine when he meets her during a suffragette protest. Unfortunately he's married to someone else by this point: the flighty socialite Sylvia (Rebecca Hall), whom he met in one of the flashback sequences and with whom he had a fruitful sexual liaison in a first-class railway carriage. The couple have a son but Tietjens doesn't even know if the lad is his, so he tells him a story about his childhood in Yorkshire – and then sends him to live there. And despite Sylvia being in the habit of cuckolding him with shallow pretty boys called things like Potty, he won't divorce her out of a sense of honour. Some men are like that.

Cumberbatch's physical oddness, his gravity and his Etonian drawl make him perfect for the role of the thoughtful, upper-class Tietjens, and he's never less than captivating.

Director Susanna White delivered a slow, maudlin opening episode with one beautiful set-piece scene – Christopher and Valentine, lost in the fog on Midsummer's Eve – and built in the filmic equivalent of lay-bys so that we could stop and enjoy the rich Stoppardian dialogue. "Kiss her fingertips for me," purred Roger Allam's General Campion, "she's the real thing." Lovely stuff.

That said, it's a brave decision by the BBC to pitch this wordy, worthy series into the froth of the Friday-night schedules – and star quality alone won't keep its head above water.