Tonight's the night for Larry King as 25-year reign comes to an end

US TV's most revered talk show goes out for the last time this evening, making way for Piers Morgan

He is from another era of current affairs television and tonight that era will end. When the lights dim on his desk this evening, Larry King, the primetime interview host for CNN for the last 25 years, will hang up his trademark braces and cede his throne to the British talent show judge and former editor Piers Morgan.

With Mr King, 76, will vanish an interviewing style that to some had become outdated long before now. You don't need a Jeremy Paxman when your guest is Jon Bon Jovi but arguably you do if it's Vladimir Putin, the Prime Minister of Russia, or Tony Blair. (All three have been on in recent weeks.) Laconic, if not sleep-inducing, King has always put the ease of his guests above investigative questioning.

That Mr Morgan plans to do things differently with his programme, Piers Morgan Tonight, when it debuts in January, is hardly a point of speculation. Being a prince to the departed King apparently doesn't interest him. The programme will be "exciting and slightly dangerous", he said recently.

"The format, everything, will change. I'm not just going to be another man sitting in the CNN studio wearing red braces. What I would say is that there will be significant format changes, and the show will look and feel different and distinctive to Larry's. I don't want to copy him because he's a legend. You don't follow Sinatra at the Sands and try and warble My Way."

The handover is a gamble for CNN and Morgan. Hardcore King fans will even mourn the map-of-the-world in tiny lights that has been King's backdrop. While final details of the new format are still to be unveiled, off-the-cuff remarks from Morgan at a London party have already ruffled feathers. He served notice that Madonna will not be invited on to his set. She "is so boring," he reportedly declared. "She's too vegan for TV. We have Lady Gaga now so Madonna is banned from my show." Not Larry's style at all. King estimates he has conducted 50,000 interviews over the span of a career in radio and TV. CNN had barely got off the ground when 'Larry King Live' debuted in 1985, providing the network with some gravitas - until 1996 it was produced in Washington - as well as ratings. Every American president made the pilgrimage to King from Nixon to Obama. But what distinguished King also was his ability to switch between a world leader one moment to a soap opera starlet the next without grinding a single gear.

His vintage period was perhaps in 1992 when a certain Texas businessman called Ross Perot announced his run for US president on his set and returned repeatedly during that year including one night for a face-to-face debate with Al Gore, the running mate for Bill Clinton, about the merits or evils of North American free trade. That one show drew 20 million viewers, breaking a record for CNN.

But the ratings began slipping steeply for King several years ago as he faced competition in his 9pm timeslot from other cable news anchors who took precisely the approach he avoided, wearing their political opinions loudly on their sleeves and probing and prodding where King would just smile.

"I ask short questions, I have no pretence at intellectuality, I don't pretend to know it all," King once said of his style. "Not, 'What about Geneva or Cuba?' I ask, 'Mr. President, what don't you like about this job?' or 'What's the biggest mistake you made?' That's fascinating".

Talking this week to the New York Times he lamented how things on primetime have changed. "If you look at media now all the hosts of these other shows are interviewing themselves," he said. "The guests are a prop for the hosts on these cable networks. The guest to me was always paramount."

He assuredly has his admirers, among them Mr Perot. "I consider Larry one of a kind, absolutely one of a kind," Mr Perot said this week. While other television interviewers "will interrupt you if you're not saying what they want you to say," Mr. King will "let you finish what you're saying", he said.

CNN is giving the veteran a strong send off with special guests all this week ranging from Barbra Streisand (whom he first interviewed in Florida when she was a struggling bar singer in Miami) to Susan Boyle and Conan O'Brien. Who will be on hand for the last show tonight is a closely guarded secret.

Chatshow gold

Ross Perot and Al Gore, 1993

A record high in viewer numbers for CNN – even though the debate was about a North American free trade agreement. "We make the best tyres in the world," claimed Al Gore, "but we have a hard time selling them in Mexico." King responded: "So he'll make more tyres?" Such exchanges enticed 20 million people to switch on. King later claimed that President Clinton had told him that the free trade agreement would not have passed without the show.

Howard Stern, 1988

Larry King held his own as the right-wing shock jock came on the show, tried to make him smoke a cigarette and poked fun at his abilities as a broadcaster and networker. "You're just a radio guy with a cable television show," Stern told a chuckling King. "We're not friends... you say you're friends with everyone."

Jerry Seinfeld, 2007

Seinfeld was exasperated when King asked whether his top-rated show had been dumped. "You think I got cancelled? I was the number one show in television Larry... Do you know who I am?"