When I was still at school in the mid 1960s I lived in West London near the river Thames. A good friend had become involved with a restoration project on an old barge moored by Chiswick Eyot (pronounced "eight") where there were some moorings. The restorer (I suppose, properly called the Bargee) was a young man recently employed by the BBC at Bush House in what had become the "BBC World Service". He had recently been trained to speak in front of a microphone to a worldwide audience, and had some interesting stories to tell.
In those days the quality of microphones was not what it is now; the radio transmission was weak in many areas; and the quality of receiving equipment was for many people very basic. Add to all that the fact that, while much of the overseas audience were expat Brits, for many others English was not their first language. While broadcasts were made in many languages, English was the core of the service, and that was the language used by my contact.
For these reasons it was important that the people in front of the microphones spoke as clearly as possible: neither too quickly nor slowly; neither too loudly nor softly; at a steady pace and level; and yet somehow natural and friendly. But how do you teach people to achieve such a meticulous standard of presentation, day in and day out? The answer was to train people to speak "as if to your favourite aunt". It being assumed that this respected and ancient relative (anybody over the age of forty was considered ancient in those days, or perhaps that was just me), whether real or imaginary, would swiftly condemn any garbling, mumbling, shouting, hesitation or being spoken to like a fool.
Among broadcasters this mode of presentation became more an ingrained habit than a performance, so it thus became common practise for them to describe their work in front of a microphone as "talking to Auntie". My contact, in particular, was part of a 24-hour service and worked various strange shifts to suit programme schedules. So (no doubt in common with others in his line of work) he would excuse himself from social events by explaining that he "had to go and talk to Auntie". By similar means the sobriquet "Auntie" had already been robustly established across the country, although few people ever understood why.
Soon after I graduated and started work as as a development engineer, I was asked by someone what I did. When I said that I worked "for Ferranti" I was misheard and asked what it was like at the BBC!
Nowadays, while the presentation style, clarity and use of language varies greatly among the BBC programmes, those of news, factual items and links has remained generally at a very high standard: the material is still clear and intelligable to people both young and old, and to those who do not have English as their native language. Whether we agree with the pitch and accuracy of the content is perhaps another matter, but it would be of interest to know how the standard of presentation is maintained at the beginning of the 21st century when the epithet "Auntie" seems hardly used any more.