Who Do You Think You Are? - Sarah Jessica Parker, BBC One

American television's desire to upgrade the BBC’s Who do You Think You Are? into a prime piece of emotional real estate was never likely to meet any serious resistance.

Even stripped of the stridently Hollywood voiceover that teed up the US version of the show when it first aired on NBC back in March - “To know who you are, you have to know where you came from”, it boomed over a slo-mo montage of Olympian hugging - last night’s tweaked version, with a new, subdued British narration, told us more about US TV and America’s relationship with its own history than it ever did about its subject, Sarah Jessica Parker.

The peculiarly intense reaction of human beings communing with old family ghosts is, I suspect, a universal one, and the narrative arc of the show remained essentially unchanged. Celeb embarks on a “life-altering journey into their personal history”, which entails jetting off to various historically charged locations to meet archivists, genealogists and local historians whose sexily rumpled paper trail leads to telegenic enactments of despair, euphoria and, ultimately, deep and humbling self-reflection. Who do You Think You Are? is like Anneka Rice’s Treasure Hunt, only instead of winking limericks for guidance we have stained parchments, old census data and dry BMD stats.

In these telly-savvy days, we’re well aware that the show is in essence a cleverly constructed confidence trick: the producers need to know the ending long before they start, and the skill lies in leading us, and the celebrity, through each stage as though blindfolded. Nevertheless, Who do You Think You Are? at its best is a very human detective story with genuine emotional investments at stake.

It was fitting that Sex and the City star SJP fronted this inaugural attempt (there are six more to come in the series, including Susan Sarandon, Spike Lee and the show’s executive producer, Lisa Kudrow) to import one of the Beeb’s most successful recent programmes. The appearance last year of her SATC co-star, Kim Cattrall, on the British version defined all that is compelling about the show. Liverpool-born, Cattrall discovered that her grandfather was a bigamist who abandoned her mother and aunts when they were children to live with his second family in a small mining village in County Durham. They never heard from him again. It was a small, intimately sad story with huge repercussions for those involved, and it made for utterly gripping television.

Last night’s exported version was thin gruel by comparison, and not just because the US version cut the action from an hour to under 45 minutes and was less keen on the forensic detail than fanfaring the inevitable moment of “closure”. So what did we learn? Less charitable critics may well hypothesise that all available visual evidence suggests that Sarah Jessica Parker’s genetic line started with Seabiscuit, but it transpired that she’s a mixture of Jewish-German on her great-grandfather’s side and original New England settlers on her great-grandmother’s.

The maternal line was the only avenue explored, which led to the most intriguing question raised by the programme: never mind the ancient ancestors, what about the father? Not only was he never seen, neither he nor his side of the family were ever even mentioned. There is, I’m sure, a compelling tale behind his absence, but this clearly wasn’t the place to air it. Family history only becomes entertainment, after all, when the potentially harmful current of a faulty connection has been earthed. Nothing here threatened to get too close to any live wires. 

So instead we travelled back to the decades immediately following the Mayflower landing. One of SJP’s forebears turned out to be Esther Elwell, arrested on suspicion of witchcraft in the Salem Witch Trials of 1692 but spared execution by a very timely stroke of good fortune. Cue much weeping at tombstones, righteous liberal anger and a healthy dose of guilt. All sturdy Who do You Think You Are? staples. 

Another, more recent antecedent was John Hodge, who travelled from Cincinnati to California to become a miner during the gold rush, but died in 1850 before he struck lucky, leaving behind the two-month-old baby he never met. His story, opined SJP, was simply “extraordinary”. Really? Pretty typical, I'd have thought, but that didn't stop her repeatedly exclaiming the surname “Hodge” as though it were her own personal Rosebud.

Indeed, she seemed in a permanent state of “Wow” at the very notion that she had any ancestors at all. The relationship between Americans – products of a still-young country founded on immigration - and their own history is markedly different from that of the British to theirs, and last night’s show illustrated this point above any other. Because two of her many ancestors intersected with two major events in the nation’s past, SJP – who started out with some certainty describing herself as from “immigrant” stock - suddenly felt as American as apple pie, while her very likeable mother neatly tied up her journey as “a very American history”. And it was, although possibly not in the way either of them imagined. After all, to travel, as Hodge did, from Ohio to El Dorado remains the symbolic dream of every son and daughter of Uncle Sam.