WORLD: Stuart Elliott in America.(advertising )

When the HBO cable network showed the US the final episode of Sex and the City on 22 February, a month before the UK will get to bid farewell, it was the end of an era - and the beginning of a new one. The reason?

The conclusion of the sitcom after six seasons crystallised profound changes Madison Avenue must heed or face being marginalised the way Carrie and her friends shunned toxic bachelors and modelisers.

For one, the ratings record set by the last show - 10.6 million viewers, almost 38 per cent more than the previous high, 7.7 million - underscores how the US now watches TV far differently from before. In the bracket of demographically desirable viewers aged 18 to 49, Sex and the City was the night's top-rated show, besting everything the broadcast networks had to offer even though they're seen in more US households than HBO.

And because HBO is a pay-cable channel without commercials, many of the best and brightest prospects for marketers' wares were totally unavailable to them on one of the most-watched nights of an important 'sweeps' months, when ratings help set ad rates.

That brings up another way that Sex and the City has changed the paradigm.

While agencies and advertisers struggle to determine how to brand entertainment fare and integrate products into programming, the series' producers deftly did just that by including totemic elements of big-city life in episodes, to serve as shorthand for the characters' lifestyles.

So intrinsic to the plots were the products that half-a-dozen brand names turned up on a list devoted to aspects of urban culture the series 'made us appreciate more', as compiled by ...