As a sign of just how prevalent this is, Robinson points out that even Princes William and Harry can be heard talking this contemporary RP that is verging on “Estuary English”. Indeed, at the time of the Royal Wedding, Robinson noticed that Kate (now the Duchess of Cambridge) spoke with a slightly more polished, conservative RP accent than her husband – perhaps an ironic consequence of the snobbery surrounding her lowlier origins, and her nerves at appearing on public display. “If you move up a social set you have to try harder to use more prestigious forms,” he says. If you watch the clip below you may see what he means.

It’s not so surprising that younger people might adopt some of the tones they hear on the streets – perhaps as a reaction against their upbringing. “There are these things we might do to seem cooler and trendier, but which we would drop when we get older,” says Robinson.

You may not, however, expect to find the same traces in an 89-year-old monarch. Yet Harrington’s studies have shown that even the Queen’s accent has subtly shifted to a more standard, “middle class” Southern English accent over the decades. Where she once said the word “lost” with the same vowel sound as “law”, it is now closer to the more common sound you may hear when Londoner Adele sings "I ain't lost, just wandering"; family is no longer pronounced “femileh”.

Just listen and you might be able hear a subtle but noticeable difference. Compare, for instance, how she pronounces “my own family often gather round (or, to approximate the way it sounds to my own working class ear, “my own femileh awften gether rownd”) in the first televised Christmas Broadcast of 1957…

… with the way that she says “I have been warned I may have Happy Birthday sung to me more than once or twice” in the 2015 Christmas Broadcast.

Even the simple phrase “very, Happy Christmas” at the end of the broadcasts reveals a shift with time. Here she is rounding off that 1957 broadcast:

And here is the way she finished it in 2015:

Harrington is sceptical that the Queen took some kind of elocution lessons in a conscious effort to sound less upper class. His analyses of the Christmas Broadcasts suggest the vowels slid slowly, almost imperceptibly from year to year – whereas if she was deliberately trying to emulate her subjects, then you would expect to hear a more abrupt shift.

Instead, he thinks an answer comes from some interesting recent psychological studies looking at the art of conversation. Various experiments have found that each time we speak to someone, our accent moves very slightly to match theirs, perhaps an unconscious effort to build rapport. There is also some evidence that it improves your comprehension of what they are saying. Importantly, the effects lingered after the subjects had said their goodbyes. “If you measure their speech you often find that they sound very slightly more like each other after the conversation than they did before,” says Harrington.