I miss the 'pea-soupers' of my childhood, when everyone in towns and cities burnt crude coal for heating, and Battersea Power Station belched out sulphur over all London. They were so yellow that they were almost green, and as a non-asthmatic child who did not understand what these smogs contained, I loved the dramatic way that they changed the landscape.
There is a Hollywood version of a Sherlock Holmes film where Holmes and Watson leave the Baker Street apartment to go on a mission and step outside into a thick, London fog to catch a cab.
In the picture, the fog serves to indicate to any Californian who is not paying attention at the cinema that the scene is, indeed, set in London. Anyone who has ever visited the area around Picadilly Circus between about 1960 and the present day will have seen London Fog sold in cans at tourist shops. Other clues (for those who do not possess Holmes's super-human powers of deduction), include the blast of a ship's fog-horn which sounds as if it is moored up in the next street.
There is another audio device in the film which helps the average American viewer to firmly grasp that the scene is set at night, and that is the sound of cicadas chirruping away on the nearby Baker Street lamp-posts on the dark and chilly night.
Cinema-goers to this picture are asked to suspend their disbelief in one area, however. Nigel Bruce who plays Dr Watson next to Basil Rathebone's Holmes goes through the entire winter of the film with a richly brown and well-maintained suntan, and there is no mention in the plot of his having recently returned from India to explain it, so I suppose it is the real thing and acquired by lounging around by his Bel-Air pool between takes. I suppose the beads of sweat on his forehead are because of having to wear a thick tweed coat in 90 degree heat also, and not the after effects of a dose of malaria picked up in India. I know this isn't the first time I have mentioned these things, but I love that scene so much that I want to keep remembering it.
I remember driving the 30 miles back from London one night with my parents through a 'pea-souper' fog, and it was so thick that my father had to get out of the car every now and then to check where the edge of the road was. The technique for driving in fogs like this is to straddle both wheels over the white line in the middle (if there is one) and keep your eyes fixed 10 feet ahead incase another car is doing the same thing in the opposite direction with it's lights dimmed like yours.
A friend of mine who was an experienced mountaineer was once in charge of a party of schoolboys who were going for an over-night hike up a mountain somewhere in Wales (I think). A dense fog settled on the hillside as they made camp and after it got dark, one of the boys went out to have a piss nearby. After quite a while, he didn't return, so the rest of the lads and my friend started calling for him so he could find his way back. They called for him virtually all night, but he didn't return.
In the morning, the fog cleared as quickly as it had settled, and they found the boy - dead from exposure - lying in a small hollow a matter of about 20 feet from the camp. The poor lad had wandered around completely disorientated for ages, then had given up and tried to sleep in as sheltered a spot as he could find.
I saw the classic scene about two days ago - a smallish girl holding onto the hand of a stranger in a crowded shopping precinct and crying because she had lost her parents. In the time it took for me to see her start to cry from a distance of about 20 feet, then walk up alongside the little drama, she was reunited with her mum and dad again and was sobbing in the arms of her mother. Those 20 seconds of separation were very real to the little girl and that was all it took to convince herself that she would never see her parents again. They were only 20 feet away from her, but they might as well have been on the other side of the earth.