This week my friend and co-presenter Hermione Cockburn dons her waders and sets off intrepidly into the lowlands of Scotland to hunt for gold (Radio 4, Wednesday, 9 p.m.). I wish she had asked me to go along, for she claims to have found five great chunks of the stuff in the Mennock Pass, and is thinking of retiring on the proceeds, although I am not convinced it will keep her in the style to which she would like to become accustomed.

Apparently much of Scotland is paved with gold, or at least in many of the valleys there are tiny specks hidden in cracks in the rocks in the icy streams, and if you know where to look you may strike lucky and make your fortune.

Gold is the noblest of metals; chemists have difficulty making it react with anything. As a result it lies around in the ground as the shiny metal, which is unusual; almost all other metals have to be extracted from their ores, and in many cases this is a difficult process. Gold is also rare and a lovely colour, which is why it has always been prized and loved, and often used as a form of currency.

The metal is extremely dense; a chunk of gold the size of a sugar lump would weigh as much as ten sugar lumps, where iron would weigh three and lead six. This is why panning works. Take a handful of grit from the bed of a stream, put it with a bit of water in a frying pan and swirl it about, and any gold in the grit will sink to the bottom. So you can carefully pour off all the grit except for the very bottom bit, and there you may find the glimmer of gold. That also is why particles of gold tend to get down to the bottom of cracks and crevices in the streams.

Don’t get too excited though. Hermione’s five pieces were actually four specks, and only one that could reasonably be called a nugget, and the total value of her find was probably less than £50. Gold may be scattered all over Scotland, but it’s thin on the ground – in fact so thin that they say Scottish gold is five times more expensive than any other gold, because it’s so hard to find.