This was 30 years ago though. Then it was a criminal offence, though as you say people didn't get sent to prison unless they egregiously failed to pay the fine.
Yes, technically it was the wife's responsibility to get the license, but if her husband usually did it and forgot, the wife would get the conviction - the same as the 16-year old in the example who probably wasn't in charge of paying for it. My point was that the bullyboys felt that fining wives because their husbands hadn't got the license was easy money, and it would seem their tactics haven't changed much.
We get the threatening letters for an unoccupied static caravan, and I'm really hoping a precious little "officer" with a "detector van" shows up so I can tell him where to go, and how far he can shove his inspection. I can't be bothered to phone to inform them we don't need a license, partly because its not my job, and partly because when I did once, the letters stopped - for a year or so. Then it was back to the same old same old. They must have spent loads on letters.