For UK fans of the celebrated TV crime series set in New York, Law & Order, Friday 10 February was a very peculiar day. One of the most famous episodes of the original US series, "Mayhem", first shown in 1994, was broadcast at 4pm on the digital channel FX. Then, at 9pm, ITV transmitted its own London-based version of the same episode, retitled "Dawn to Dusk": part of the most recent batch of the thirty-nine scripts from the US show that have been reworked for the UK. As one of the characters in "Mayhem" says, it was déjà vu all over again.

For those of us who have watched every episode of the US show, some many times (I must get out more), this coincidence was a chance to reflect on the differences between US drama and UK drama, in the very specific framework of an overt remake. Are they cultural? Are they structural? Are they financial? Here, the reason for US superiority could not be better writers, a better format or a bigger budget, not least because the Law & Order: UK exercise has been much more tightly controlled than other remakes. The owners of the show, Universal (who bought the US production company, Wolf Films, many years ago), have always jealously guarded the franchise: no doubt one of the reasons why Law & Order lasted twenty seasons on US network television, the longest-running crime drama series of all time, with 456 episodes.

Dick Wolf, the creator of Law & Order, had come up with the format so as to take advantage of the popularity that thirty-minute network shows seemed to enjoy when they were later syndicated to independent US stations. He saw the first half of his hour-long episodes as being devoted to two detectives trying to solve a crime, and the second half to two prosecutors in the District Attorney’s office, trying to convict those accused. Perhaps, in syndication, stations could choose between showing the two halves separately, or the complete hour, so increasing his potential earnings.

Wolf persuaded the Fox network to commission a series of Law & Order in 1988, but its president, Barry Diller, changed his mind. Wolf then made a pilot for CBS. They declined to go ahead with a series order, so he then sold a full series to NBC on the strength of the CBS pilot. Although the drama clearly owed much to precursors like Hill Street Blues and Arrest and Trial, a number of features gave the drama a real distinctiveness: its combination of detectives and prosecutors, its hand-held shooting style, its minimal use of incidental music, its quasi-documentary white-on-black captions (marked by a two-note music sting) declaring the location of the next scene, and its regular use of walking shots as witnesses and suspects were interviewed by the investigators. So, of course, did the New York street settings for all the exteriors. Mayors Giuliani and Bloomberg both appeared as themselves, as did the famous civil-rights lawyer, William Kunstler. Giuliani’s actress ex-wife, Donna Hanover, featured as a judge, as did writer Fran Leibowitz. It was not just the stories that were "ripped from the headlines".

The cinematographer for the pilot was asked to watch Gilles Pontecorvo’s celebrated movie The Battle of Algiers, so as to understand how a documentary feel could be injected into drama. There are no set-up shots, no establishing shots, and no recapitulations. The pace is frenetic. Apart from an opening sequence revealing how the crime in question was discovered, every scene contains either the detectives or the prosecutors, or both. Nothing extraneous intrudes - "no fat", in Wolf’s words. A single episode can contain forty or more scenes.

When the BBC broadcast the second series of its award-winning drama Criminal Justice - the account of a single crime which meandered across five nights of hour-long drama - a Law & Order episode shown the same week on Sky One squeezed a very similar story into the standard forty-four-minute running time.

The "look" of Law & Order is another characteristic. Wolf was determined to match the grainy quality of his favourite documentaries, desaturating the final colour print for transmission. Before the first series aired in 1990, he asked the president of NBC Entertainment, Brandon Tartikoff, to broadcast the programme in black-and-white for best effect. Tartikoff smilingly offered to put up a caption inviting viewers to turn their colour control all the way to the left. Wolf conceded defeat: he had taken his homage to Jules Dassin’s classic 1948 film noir, The Naked City, as far as he could.

Lost in transposition

Law & Order: UK faced a series of obvious problems. In New York, the District Attorney is an elected official, so politics plays an explicit part in the way the DA’s department is run. The Crown Prosection Service (CPS) and other equivalents across the UK are completely non-political. In the US, plea-bargaining is an everyday event, usefully hustling the TV action along. Plea-bargaining is extremely rare in the UK. Also, although solicitors can these days represent their clients at trial in Crown Court and the High Court, this is not the usual practice: whereas in the US there has never been a division between solicitors and barristers, so lawyers move seamlessly from the interrogation room to the courtroom. When that happens in the UK version, it always jars.

The arraignment court, with its own judges, is also a bedrock feature of the US system, with a succession of accused people being wheeled in to enter a plea: the familiar cry "docket number 54321" (or whatever number) regularly marks the handover from police to prosecutors in each episode. First appearances in UK courts are distinctly undramatic. All these differences of procedure forced changes in every UK version of the scripts.

There is no doubt that Law & Order: UK has been successful by many standards: it has been regularly recommissioned, and has been sold overseas to eighteen territories, including the US, where it is carried by BBC America. And for the most part, the UK producers have stuck to the format and the style of the original. However, there have been departures from the Dick Wolf blueprint. There is more incidental music. There is far more "back story" about the lawyers and detectives: something Wolf was intent on excluding, however much the audience might be used to "going home" with the characters in more soap-driven dramas. Only in series twenty of the US version was there any sustained coverage of one long-serving character’s "back story", as she underwent treatment for cancer.

The UK show deploys the "walking twos" and even "walking threes" so familiar from New York, as characters discuss next steps whilst on the move; but in London, this too often constitutes various moody shots near assorted London bridges, often remote from both the police station and the action, resulting in a fatal loss of pace. The filming style is also fussier, with one episode including a failed attempt at a comic character, and another a distracting element of cross-cutting.

But "Dawn to Dusk" exposed the deeper problems with transposing such a well-rooted drama. The UK is good at producing leading actors and actresses: these days, no US drama seems complete without a Damian Lewis, a Tim Roth, a Hugh Laurie or an Alfred Molina - even Law & Order cast the excellent Linus Roache as the main prosecutor for its last few seasons. However, depth of cast is another matter.

Only Bradley Walsh - former comedian, former star of the longest-running UK soap, Coronation Street - convinces amongst the leads in Law & Order: UK, playing the role of Detective Sergeant Ronnie Brooks: a persuasive version of Lennie Briscoe, the role created for Broadway song-and-dance man Jerry Orbach in the US. Supporting cast is even more disappointing.

In New York, there is a huge pool of talent from which to draw: from Broadway, off-Broadway and off-off-Broadway. Any theatregoers perusing their Playbill will find the cast CVs making regular reference to the "L & Os" - Law & Order and its various spin-offs, including Law & Order: Special Victims Unit (still on air), Law & Order: Criminal Intent (final season currently being shown in the UK on the Universal Channel), and Trial by Jury and Conviction (which both only lasted one season). One actress claimed to have played a dead body in three separate episodes.

Watching reruns of the US series offers added pleasure for those who enjoy spotting the rising stars in minor roles: such as a young Philip Seymour Hoffman in his first TV part (still Philip Hoffman in those days), a young Maura Tierney (before she became the female mainstay of ER), William H Macy (who appeared in the pilot as WH Macy) and Lauren Ambrose (as a troubled teenager, presaging her role as Claire Fisher in Six Feet Under). A small role in "Mayhem" is played by the young Robin Tunney, these days the female foil to Simon Baker in the long-running drama series, The Mentalist.

A no-contest contrast

In "Dawn to Dusk", every supporting part compares unfavourably with "Mayhem". But the problems go deeper. In both versions, two uniformed policemen discover a parked car early in the morning, with the driver seemingly asleep. Opening the driver-side door, they realise he has been shot through the head. The "Mayhem" location was a New York park, allowing an eccentric bag-lady, claiming to be an eye-witness, the chance to play a couple of sparky scenes with the detectives. In "Dawn to Dusk", the victim is found outside a featureless City office block, and the eye-witness is an anonymous hung-over City worker.

A second (unrelated) homicide happens close by to the scene of the first, with the detectives called to the scene as it occurs. In the UK version, of necessity this has to happen in another City office: two brothers who own a failing business have had a fight, one using a paper-knife to inflict a stab wound, the other using a heavy paper-weight to knock out his sibling, who later dies from his injury. In "Mayhem", the victim, who lives close to the park, is a womaniser whose penis has been cut off by his irate wife: he, too, dies in hospital, from shock and blood-loss. Presumably this was too "New York 1994" to be used in "Dawn to Dusk", but it was certainly far richer as a source of drama and dialogue. The feminist defence lawyer arguing self-defence by an abused wife is granted two lively scenes in "Mayhem". The UK version is pallid by comparison.

"Mayhem" was chosen as a title because it dealt with five homicides in a single day: imaginable in 1990s New York, maybe, but scarcely in modern London. So, two of the killings are excised in "Dawn to Dusk". The first is of a store-owner shot dead by a crack-head for the sake of the till’s contents; the second is of the store-owner’s killer, murdered in turn for his stash and cash.

In "Mayhem", the killer of the crack-head is caught by the detectives, but puts up resistance both at the scene and subsequently at the precinct. He arrives for arraignment sporting a black eye and bruising, and promptly claims to have suffered from police brutality. It is another humorous moment in an increasingly dark scenario.

In "Dawn to Dusk", the cry of intimidation is raised by the accused from an entirely separate case, and is spliced into the main storyline; perhaps as a means of making room for more screen time for the lawyers ("Mayhem" had been an unusual episode of Law & Order in devoting most of the action to the detectives).

This awkward insertion requires two additional diversions of time: a wholly unconvincing "race" to establish whether the interrogating officer (by a strange coincidence, Ronnie Brooks’s new partner in the Murder Unit) did or did not intimidate the accused into confessing his crime; and (leaving that issue unresolved) a parallel blackmailing threat by the CPS to withdraw future prosecution work from the defence barrister’s chambers, unless the accused is persuaded to drop his claim, on the grounds that it lacks credibility (rather like the storyline).

An unfortunate by-product of this scripting aberration is the loss of the identification parade for the suspect accused of committing the first homicide (an innocuous looking individual who wears heavy-rimmed glasses, as shown in the photo-fit based on eye-witness descriptions). In "Dawn to Dusk" the parade is never seen, only reported.

Such a glaring breach of standard narrative practice - "show, don’t tell" - would surely never have been tolerated in Law & Order. In "Mayhem", the line-up is a subtly important scene, as the girl who had been in the car with the victim first picks out our suspect, and then settles on someone else, also wearing heavy-rimmed glasses. The suspect is duly released, without ever agreeing to provide an alibi for the time of the park shooting.

By now, we know that Ronnie Brooks has box tickets for an important West Ham United football match, echoing Lennie Briscoe’s anxiety to finish work in time to get to a New York Knicks basketball game, for which he has precious court-side seats. The UK version follows "Mayhem" in substituting a ticking digital clock for the familiar "ching-ching" accompanying the captions announcing scene changes: we realise that the chances of getting to the game are diminishing with each new development in the main case.

The suspect in the first homicide (called Scott Hexter in the US, but - puzzlingly -Roland Hextor in the UK) is rearrested when it transpires that his car had been stopped for speeding near the location of a previous murder, only minutes after it had happened, and where a similar weapon had been used. He still refuses to say where he had been at the time of the first shooting, and in the arraignment hearing (in the US)/plea-management hearing (in the UK), he is remanded in custody.

Eventually, his mother explains (in both versions) that it was she who was driving his car at the relevant time. Then the reason for his reluctance to admit his whereabouts is revealed: a covert gay relationship. In the UK, a neat piece of plotting by Richard Stokes (series producer, and adapter of this script) has Brooks discovering CCTV footage of Hextor boarding his regular ferry the previous evening, alongside a well-dressed man. Hurrying to the ferry terminal, Brooks quickly finds the man about to board, at the same time of departure. He readily provides the missing alibi. Brooks then sets off to the remand prison to ensure Hextor’s prompt release, leaving his partner at the police station, baby-sitting his own child after his estranged wife arrives there and dumps the boy on him (another unfortunate dip of the toe into "back story").

The football match is long over by the time Brooks arrives at the remand prison, but he has arranged to view a recording, to be watched without knowing the result. However, Hextor has seen the game on television, and lets slip that the Hammers have lost 2-0. The episode ends on this wry note of bathos.

In "Mayhem", by contrast, once Briscoe and his partner confirm Hexter’s alibi, they set off to Rikers Island to ensure that Hexter is released promptly, so that they can escort him home. He is not ready when they arrive. Then they are told he is in the infirmary. When they reach the infirmary, they see a curtained area. Behind the curtains, they find Hexter’s body laid out. Another remand prisoner attacked him with a sharpened toothpick, in order to steal his baloney sandwich, and he has died from the stab wounds.

The shocked detectives return to the precinct station, aware that their dogged pursuit of a "man with heavy-rimmed glasses", together with Hexter’s reluctance to out himself, have led to a wholly unnecessary death. As Briscoe checks his watch, his partner notes that the basketball game will be into its final quarter. Ever the optimist, Briscoe speculates that there might be overtime, and the pair set off for Madison Square Garden. It has been another long day in the naked city.

An oceanic gap

Is it fair to compare the high-octane drive of "Mayhem" with the more languid "Dawn to Dusk"? Perhaps not, but for the fact that for at least a decade the widely-accepted view has been that US TV drama has left UK series drama (with one or two exceptions) far behind. The writing is more disciplined, the production teams more skilled, the directors less indulged, the casting in depth more convincing, and the overall level of ambition significantly higher. This applies not just to series on HBO and its cable rivals, but increasingly those on network channels, too.

The structure of TV production, distribution and broadcast in the US is more conducive to the creative community than is the UK set-up, where the broadcasters and commissioning editors have too much control. In the US, the "show-runners" - the likes of Dick Wolf - have far more autonomy, linking up with international and domestic distributors to co-finance programmes with the networks. Competition for talent - producers and writers - is intense. Wolf - having placed Law & Order in turn at Fox, CBS and NBC - almost worked a deal to take the show to ABC after NBC finally cancelled. Law & Order: Criminal Intent found a home on the TNT network after NBC failed to renew.

Creative cultures are important. So are structures. Downton Abbey has been a major success for ITV, and represents a particular type of UK storytelling very well. It is produced by one of the longest-established UK production companies, Carnival - which has been owned, since 2008, by NBC Universal, owners of Law & Order. It is Universal’s ability to invest - alongside ITV’s UK broadcast fee - monies leveraged against overseas sales that have funded the lavish look of Downton Abbey: the best of both worlds.

However, comparing Law & Order and Law & Order: UK, we see what happens when the creative culture falls short. Having been in charge of three broadcasters that acquired Law & Order for showing in the UK, I feel I really understand its qualities. Even with the original episodes as a guide, not one of the UK adaptations has actually improved on the underlying script, in my view. Perhaps London crime today is "cooler" than New York’s in the 1990s: eighteen years separate "Mayhem" from "Dawn to Dusk". But the contrast in creative skills is the most important difference. Any further chance directly to compare original episodes and remakes will only confirm the size of the gap.