David Letterman Will Be Sorely Missed

As Rolling Stone Magazine put it, when David Letterman began, the most popular show on television was Dallas and the Fonz was still on air.

His career stretches back to another time, another era.

And yet when you watch him in the 80s or the 90s or last week, his act changed little.

If you can call it that.

Because Letterman's genius was his subversion of the format from the very beginning.

It is what made him compelling to watch and allowed him to last so long.

Letterman never seemed happy with the chat show programme he found himself in. He was too sharp for that.

:: Letterman's Top 10 Late Show Moments

The pitch to the viewer is simple.

You are being given privileged access to a conversation between celebrities, with their guards down.

You can laugh along with them and join the party, courtesy of your host.

From Johnny Carson and Jay Leno to Jimmy Fallon, that has been the deal.

David Letterman was never comfortable playing that part.

Sure he would feed his Late Show guests lines, but equally often he would not, quite happy to watch them talk themselves up an embarrassing cul-de-sac if the mood took him.

If he did not agree with a guest he could be merciless.

His treatment of Bill O'Reilly, from Fox News, is a master class in giving your guest enough rope.

Listen to O'Reilly's mouth drying with nervousness, gasping for air as Letterman hands out the slack.

Like blander chat show rivals, he might laugh along with his guests, but was equally happy to poke fun at them.

When Justin Bieber told him he was not planning to tattoo his arms like the 'Sixteenth Chapel', as opposed to Sistine Chapel, Letterman let the laughter roll before dropping the one liner: "Canadian high school."

His attitude did not always endear him to the network suits.

When the chat show giant Johnny Carson retired, they gave his slot to a safer pair of hands, Jay Leno, whose smooth confidence and faultless delivery could let management breathe easier.

But that also gave Letterman more street cred, and his brand the edge. It meant his appeal has lasted longer.

Television is boring if predictable. David Letterman kept us guessing. It would depend on his mood and what he made of his guest.

With him gone, comedian Tina Fey has commented: "There is no one left to be scared of. It's friendliness now."

He leaves a more boring late-night schedule behind.

For three decades he has helped America laugh at itself.

In the current era of puffed-up celebrity and social media narcissism he has been a tonic and will be sorely missed.