The Art of Conversation, Radio 4

When he wasn't getting drunk and cheating on Caitlin, Dylan Thomas, who was unfit for active service (the military kind at least), spent part of the Second World War working for the Ministry of Information writing propaganda scripts for films and radio.

And in April this year, while he was digging around at the Harry Ransom Centre in Texas, which holds many of Thomas's papers, his biographer Andrew Lycett unearthed a handwritten manuscript which had never been broadcast.

The first draft of a piece based on the dictum that "careless talk costs lives", it was presumably written to reinforce the millions of posters up and down the country that warned against loose tongues. It takes the form of a lecture from a very Thomas-like figure that spins off into sequences involving some legendary talkers, the idea being that the art of conversation is in decline. He then gives graphic descriptions of the kind of chat that can lose wars.

(The lecturer, incidentally, is played by the great Welsh actor Philip Madoc – who, for all the meaty parts he's had over a long career, will doubtless have as his epitaph: "played the U-boat captain in Dad's Army".)

The point is to rail against gossip, the "professional rumourists, the non-stop, monotonous mince and moan of those queer English natives beating across the suburban wilds their peeping tom-toms of credulity, suspicion and misinformation". And after expert parodies of Oscar Wilde and Dr Johnson, as well as depictions of struggling novelists, posturing poets and bright young things – proving the old saw that empty vessels make the most noise – the serious business kicks in.

Thomas had the very good idea of having a loud chord, a cross between Bernard Herrmann and Schoenberg, sound from on high every time there's a scrap of gossip that could have some deadly knock-on effect – like God looking down and shouting, "Shut it!" So there are two old blimps discussing the location of food caches; the vicar boasting about his son's new job with the BBC to Mrs Wharton, whose own son has had his leave stopped; and the sailor showing off to the girl he's chatting up, attempting to impress her with his stories of mine-laying (and isn't she just a bit too interested?).

With its use of sound effects and the whispering voices that punctuate the script, it's not entirely fanciful to see it as a dry run for Under Milk Wood, which Thomas worked on for around eight years after the end of the war. It's also important to note that it's a first draft, and Thomas was one of literature's great revisers – 160 manuscript changes alone were counted for the Prologue to his Collected Poems, for example. So it's fascinating to speculate what he might have made of it.