It's also the most difficult to answer. Letters on this subject received by Feedback on Radio 4 prompted the programme to dispatch one of its reporters to the BBC Newsroom at Television Centre in west London to find out more:

My own view is that the choice of stories and the order in which they are presented is based on a number of factors, which inevitably, overlap: how significant does the story feel? How interested is our audience likely to be? How new is the story? What is the context? (Not just in terms of what else is going on but also, have we done variations on this story recently?)

These considerations are combined with something more difficult to define - a journalistic instinct perhaps - in the decision-making process.

On the Six O'Clock News on Radio 4 we aim, to mangle a phrase from the New York Times, to provide all the news you need to hear. By the end of the bulletin, we want listeners to feel they know about the important events that have happened that day in the UK and around the world, and why they happened.

Fortunately, our audience is rarely shy in letting us know if that is what we have achieved.

I was sitting at my desk the other day when one of the producers pointed out that the alcohol figures we'd been expecting had just been released.

I looked up at my screen, anticipating a sharp spike in the number of people who'd died because of alcohol abuse. Stands to reason, I thought: recession, people losing their jobs, drinking to console themselves - the numbers are bound to be up.

But they weren't, in fact they were marginally down. Stands to reason, I thought: recession, people have less money in their pockets, can't afford alcohol.

Then I saw that the figures related to 2007 and I thought, stands to reason: the numbers were fairly stable, because they covered a period before the full-blown recession took hold.

However, there is another explanation - that the figures had nothing to do with the downturn. When a story as big as the economic crisis takes hold, there's a tendency to see nearly every other story within its context. But human behaviour, and by extension news, is driven by a myriad of motivations. There's a danger that we all start to view the world through too simplistic a prism.

Dominic Ball is editor of the Radio 4 Six O'Clock News.

On the Radio 4 Six O' Clock News (or simply "the 1800" as it's known within the BBC) historically, we've tried to avoid live inserts from correspondents. This is mainly because we try to create an atmosphere of calm, considered authority and we like to give the impression, at least, that everything has been prepared well in advance. It's also because taking a correspondent live shreds the nerves of both correspondent and editor.

However sometimes important news breaks so late that we have no other option. When it works well, as I believe it did with the two examples above, it can provide a wonderful sense of immediacy. That said, I'd like to reassure regular listeners to the 1800 that this is in no way a precursor to correspondents being interviewed by presenters, or, God forbid, Harriet Cass reading out texts.