A selection of images showing the history of the Christmas broadcast.

The Queen’s voice in her Christmas message has grown easier: less high-pitched, and, like that of many of her subjects, by some mysterious process, less upper-class. The happy Christmas has grown less heppy than when she first spoke to camera in 1957 from her ern herm at Sandringham, as orphan before on the wireless. Oddly, her grandfather, George V, had less of a cut-glass accent. You might think he had been brought up in Nova Scotia or some such unfamiliar province, pronouncing omen as ormen, been as bin and time as tieym.

The makers of Cue the Queen: Celebrating the Christmas Message (BBC One) had earlier tried putting the word “Speech” into the title, to suggest the name of the film from 2010 about her father’s conquest of his impediment. They decided against it, quite rightly, since the Queen delivers a message and doesn’t make a speech, even if at 3pm her pud-stuffed subjects do shout: “Turn on the Queen’s Speech.” The documentary was not just a compilation of clips from the Queen’s Christmas visitations to our firesides, and it even succeeded, against my expectations, in producing interest and tension once again from the tale of George VI’s speech therapy.

Mark Logue, in his grandfather Lionel’s consulting rooms, which the Duke of York (as he was) had attended every day for three months at the end of 1936, read from an old purple-carbon typescript describing the new King’s first Christmas message, after lunch at Sandringham: “Five minutes to go – the King lights a cigarette”. (Viewers would be aware that he would die from lung cancer.)

Then we heard the King’s own voice from that day, speaking of his father, with pauses just too long, and always at the risk of breakdown, as he applied his training to get the words out at all: “The revered… head of a great… family, his words… brought happiness.” It was moving.

The director of the film, John Hayes Fisher, also mischievously included endearing snippets of footage of the Queen at Christmas time: in 1986 saying to children gathered near the horses in their stalls at the Royal Mews: “Get bitten in a minute,” or three years earlier explaining to other little children the name of a corgi: “Dash – you know, the word you use when you’re cross.”

It was all fascinating. Our curiosity was rewarded via the access that Kirsty Young clearly enjoyed gaining to such private spots as the long library at Sandringham. The Queen is 90, our longest-reigning monarch.