World: Stuart Elliott in America

The king of late night is dead, long live the king.

That's not quite the proclamation that went out recently when NBC, the ruler for decades in American TV programming after primetime, disclosed plans to change the host of its franchise The Tonight Show by anointing Conan O'Brien to succeed Jay Leno. But given the prestige involved (not to mention the money), it's little wonder the US media covered the surprising news at the chatshow as if it were a coronation instead of a changing of the guard.

Tonight has been around for 50 years - even longer, if you count a predecessor series, Broadway Open House, which many TV historians do - and began in New York before making the move westward to Los Angeles in 1972.

Its blend of comedy, music, talk, variety and schtick, featuring the top names in showbusiness and pop culture, runs 60 minutes a night (cut from the original 90) and appears Mondays through Fridays after the NBC primetime line-up and the late newscasts on the network's 200-plus local stations have concluded.

The Hollywood Reporter estimates that Tonight, which last season averaged 5.8 million viewers a night, takes in $3.5 million a week in advertising revenues and accounts for no less than15 per cent of NBC's bottom line.

The show appeals to the younger, stay-up-later type of audience craved by many marketers, especially the beer-, car- and movie-makers.

Plus, NBC's primetime schedule for the 2004-5 season, which got under way last month, is off to a decent but far-from-stellar start. That made the network eager, even a tad anxious, to plot a placid path for the handover.

Also a factor: the knowledge that O'Brien, who currently hosts Late Night with Conan O'Brien, the talkshow that follows Tonight, was being wooed by rival networks such as ABC and Fox, which are waiting for his contract with NBC to expire in about a year. To prevent O'Brien, whose show has a somewhat younger audience than Leno's, from being filched, Jeff Zucker, the president of the newly formed NBC Universal Television Group, stepped in personally to make a deal with both O'Brien and Leno.

So a five-year contract Leno signed in April to stay the course at Tonight now becomes his final pact, with his blessing, and the expiration date, 2009, the end date for Leno's reign. When he signs off for the last time, his tenure will have extended 17 years, a short run for the likes of Queen Elizabeth II but more than four times the term of the first president Bush (and, let's hope, the second).

Though Madison Avenue likes the certainty the deal insures, others are spoofing the slow-motion succession - especially David Letterman, who lost out to Leno in 1992 to succeed Johnny Carson at Tonight, then left for CBS to start Late Show with David Letterman opposite Tonight. Letterman labelled Leno a "lame duck" and, mocking his reputation as a workaholic, declared that the five-year deadline "saves NBC the cost of a team of wild horses".

We'll leave the last word, for now, to Leno, an avid collector of classic autos, who said he'd decided to retire when he'll be 59 because "I realised I'm not spending enough time with my cars".