This is a transcript of the commentary:

That was a scene from the new British film The Brave Don't Cry, with a mining disaster as its theme. And here's the man whose job it is to see that all the details are right - retired inspector of mines Bill Withers, from Scotland.

He's come to talk over plans with designer Michael Stringer. Every set in the film is modelled in miniature before shooting. What looks OK to the naked eye may not be at all the same seen through the camera.

Want to know how to make your own coal? Here's how it's done - in the plasterer's shop. Over a plastic mould you lay plaster and canvas, layer upon layer. When it's dry, you peel it off and see the results for yourself. These sets are complete in every detail, down to the fungus on the timber. But it's not until they're seen through the camera that they'll really come to life. Michael Stringer made scores of paintings underground like this one to guide the studio carpenters and prop men.

Back on the working set, Bill Withers checks the next setup with director Phil Leacock and continuity girl Tilly Day. In a minute, the cameras will be rolling again on another scene.