Last Friday it was announced that the ABC will lose a flagship person from its flagship program. It could be a pivotal moment for the national broadcaster.

Kerry O’Brien will leave the 7.30 Report, which he has anchored for 15 years. A moment’s reflection reveals the significance of the move.

He has dominated serious daily current affairs for so long that his face, and perhaps most of all his interview style, will be part of the mental furniture for anyone who has been politically aware over the past two decades. For those who are politically engaged but yet to reach middle age, it might be hard to imagine national affairs without O’Brien’s presence.

He has not only played a key role in national politics, but also internally at the ABC. During the dark days of Jonathan Shier’s period as managing director, O’Brien was the focus point of attention  —  a symbol of the national broadcaster’s importance, and a player in the internal politics.

We now know that Shier was trying to get rid of him. Many saw the Howard government’s antagonism towards the ABC as being reflected in Shier’s hostility.

So what happens now?

For those who grew up with O’Brien, it might be hard to imagine any other way of doing flagship daily current affairs. Yet that act of imagination is now under way.  There are those within the ABC who believe the 7.30 Report is a tired format. Mark Day, The Australian’s media commentator, says as much today.

O’Brien has read Day. He told me this morning that there was a constant conversation within the 7.30 Report team about changes to format. “There isn’t a conversation you could think of about the program that we haven’t had,” he said.

And he believes “there is only so much you can do” with the format. He worries that more than tweaking might detract from the key thing — the content, and the need to report and analyse the daily news.

Yet it is clear that internally, O’Brien’s departure will provoke a review of whether modern television current affairs, and the 7.30 Report in particular, needs to change.

We have travelled a long way since the days that O’Brien sees as the genesis of today’s format — the groundbreaking This Day Tonight in the 1960s, with Mike Willesee — a man O’Brien considers the best political interviewer the country has seen — as its Canberra correspondent. Even before that there were precedents.

And what about the set piece political interview — the thing that O’Brien has so dominated and made his own? Is it still an illuminating exercise?

O’Brien believes it has become more adversarial because “we have never seen spin as institutionalised in politics as it is today”. Politicians come to the interview determined not to depart from the script, from what they decided or worked out with their advisers they would say before they left the office.

He has heard that politicians prepare and practise for an interview with him, which “I find a bit sad. If you have the material in your head and a department to back you up, it seems sad to me  that you do not have the confidence to engage in an interview in a genuine fashion”.

And he acknowledges that it has become harder to get that genuine engagement. Are there new methods? New paradigms? O’Brien is a conservative about formats. He believes there are only so many changes you can make. “There is a limit to the extent you can change it without it being at the expense of the content. The news gives you the raw material. Current affairs gives the analysis and the angles.

“You can be studio based or out in the field or a combination of both. A new personality will in itself bring changes and freshen it up.” But none of that should  dominate the prime concern — the content.

And the highlights of his extraordinary career? There are too many to name, he says. “You might ask my favourite interview, but it is like asking for a favourite book. You have a hundred.” Nevertheless, he nominates interviews with Nelson Mandela, Barak Obama and Mikhail Gorbachev. Margaret Thatcher was “very interesting”. But the interviews that “kept me sane” were those with people from outside politics — Woody Allen, or Bette Midler, who was “supremely delightful, full of intelligence and well informed”.

As for lowlights, he nominates the Shier era —  a “vandalistic period”. The damage, the bull-in-the-china-shop approach, was self limiting, he says, but nevertheless there were good people whose careers were damaged. He declines to name names.

And what of the national broadcaster’s current directions? O’Brien is circumspect. He neither endorses nor condemns current managing director Mark Scott. The ABC faces difficult challenges, difficult choices have been made and doubtless there will be more difficult choices ahead, O’Brien says. He credits Scott with “laying out a direction for the ABC”.

He will not be drawn on whether it was right to plough resources into the new ABC24 news service. There is a risk, he agrees, that it will divert resources from news gathering and content, but he won’t say it was a wrong decision.

Rather, he emphasises that Scott and management “must make sure that the demands of 24-hour news don’t stretch the resources too thin”. The ABC’s funding base is not growing as fast as the demands placed upon it. Hard choices have to be made — such as the recent attempt to make savings by automating studios. But they can then bring their own problems.

Having said all that, and while refusing to enter into the debate about whether ABC24 channel should exist at all, he has nothing but praise for the effort so far: “I think it is an amazing effort to get it up in the time they did, and the service they have produced is of very high quality.”

O’Brien has been in conversation with ABC management for some time about the need for succession planning — although my understanding is that no decision has been made about who will replace him.

It is clear that his departure will be the catalyst for some fundamental thinking about the future of the program, and its format. With the re-entry of Channel Ten into serious news reporting, there is new competition on the block. More widely, everything about how people use and engage with media is changing.

There is a mood in senior management for deep thinking about new formats. We may see something new emerge in television current affairs.

In the meantime, O’Brien’s presence at the ABC is not over. He is in conversation about a new role in 2011, but not one that will dominate his life in the way that the daily treadmill of the 7.30 Report has done.

He says he wants to give his brain a break, and then “see what comes” in the way of new ideas.

Whatever follows him, O’Brien has been a positive presence in Australian public life. He has combined steely intellect, curiosity and breadth with an ingrained integrity.

Whether or not the format he has dominated has had its day, whether or not, in this time of alleged new paradigms, there is some new and as yet undiscovered way to get politicians to engage, we must hope that whatever comes next includes a place for journalists with those same characteristics.