BBC4 has already delighted British fans of Mad Men by bringing forward the new series by six months, to September. Now viewers partial to slow-burning US dramas can look forward to Rubicon, the latest offering from Mad Men broadcaster AMC to be acquired by the channel.

Mad Men, the stylish drama set in the world of 1960s New York advertising, is nominated for 17 awards, more than any other drama, at this Sunday's 2010 Emmy awards. It has changed the fortunes of AMC (American Movie Classic), a cable channel once known for old movie repeats but now being likened to a mini HBO, the station behind The Sopranos and The Wire.

Post-9/11 conspiracy drama Rubicon is slow-paced, although that did not stop the debut episode in the US attracting 2.5 million viewers, the biggest audience for a new show in the network's history.

Its hero, a data analyst, seems to spend entire episodes lurking in dimly lit Washington libraries staring at crosswords waiting for hidden codes to materialise in front of his eyes. Code cracker Will Travers, played by James Badge Dale, is embroiled in a conspiracy that saw his boss dispatched in a train crash. Rubicon also weaves in Miranda Richardson as the widow of a tycoon whose husband changed his will to put her in charge of his companies and then killed himself.

The initial promise was that the series could stand shoulder to shoulder with such 1970s conspiracy classics as Three Days of the Condor and The Parallax View. Critics have said Rubicon is not as sexy as Mad Men, nor as brutal as AMC's second original drama, Breaking Bad, the lauded jet-black saga of a chemistry teacher with cancer turned crystal meth manufacturer. But it has confounded some US critics with its cast of shabby government underlings and its disinclination to plant a clear signpost as to where the story might be headed.

Its audience in the US has dipped, but both Mad Men and Breaking Bad started slowly and went on to build a loyal following.

After decades of anonymity, AMC saw the 2000s out as one of the prime purveyors of signature cable drama. For a long time, HBO had that market sewn up. Its slogan was: "It's not TV, it's HBO." The very name was a mark of quality. Something that differentiated it from terrestrial networks such as NBC and Fox, which still struggled to attract the widest possible audiences. But then perennial second-place cable channel, Showtime hit on its mums-with-problems formula (Weeds, Nurse Jackie, United States Of Tara).

FX, another undistinguished movie channel, took a chance with The Shield and quickly became the destination for anti-hero projects (Sons Of Anarchy, Justified, Damages).

And now AMC, producer of two prodigious series with nothing in common except their leisurely pace, has carved out its niche as purveyor of slow but endlessly involving dramas. Despite the show's Rubicon's mixed reception, AMC remains committed to commissioning original dramas. October sees the debut of The Walking Dead, a zombie thriller created by Frank Darabont and starring Andrew Lincoln. And, because its AMC, these zombies move slowly. Very, very slowly.