Nearby stands a church of one of the stricter forms of Protestantism. Just up the road begins the district of Canaan. My first thought was that the “stains” referred to were of a religious character. I was intrigued by the idea that perhaps the sign suggested that sin might be character forming.

This chimed in nicely with my recollections from an Anglican upbringing.

The story of the Prodigal Son contested successfully with my poor father who had been raised in the tradition of pre-emption from sin. He had won several prizes for rejecting the temptations of the Demon Drink and swearing Lifelong Abstinence at an age too tender even to have sampled that which he was called upon to abjure. For me, however, the idea of some wholehearted sinning followed by a return home to a hero’s welcome, while the Goody Twoshoeses ground their teeth in a corner, looked like the way to go. “No stains. No learning.”

While in this meditative phase, I confess to wayward recollection of the names of Captain Pugwash’s pirate crew, including Master Bates and Seaman Stains. What a glorious piece of subversion! That snapped me out of the religious train of thought. “No stains. No learning” was too far out of character with “The Wages of Sin is Death”; a phrase as often used to guide the errant soul under a Caribbean sun as it is outside the most forbidding, smoke-blackened, Wesleyan chapel in Oldham.

So I passed on to thoughts of an educational nature. There are also schools close by. Was the meaning of this delightfully obscure motto along the lines of “No pain, no gain” or even “Where there’s muck, there’s brass”?

Yes! That must be right. Here under blue skies, the effectiveness of learning through experience was being proclaimed. The vocational millennium had already dawned and, from the moment they could read, on their daily travels to and from school, island children were being reminded that book-learning was essentially ersatz.

I saw all and I understood all. Here, as in that other island paradise, Guernsey, there was a quota for apprenticeships. The number of plumbers, motor mechanics, electricians and hairdressers was restricted. They were among the most desirable of futures to which a child and its ambitious parents might aspire. Scarcity provided a premium and lifelong certainty of reward, denied to the run-of-the-mill manager or doctor. Even while the juvenile mind was pondering on English literature, history and geography, “No stains. No learning” was quietly insinuating the message that society depends on its drains.

I was elevated. I was inspired. Here at last was parity of esteem fulfilled, emphasising the ultimate vacuity of white-collar jobs. “The last shall be first and the first, last.” Plumbers on top. Politicians at the bottom of the ant-heap of useful service.

Then I began to worry that this might be a deep-laid plot. Were the offspring of the proletariat being seduced into remaining the proletariat of the generation to come? Was there a scheming nomenklatura, masking itself successfully as egalitarian but meanwhile entrenching its privileges?

The more I looked around me, the more this notion gained ground. The usual quality of plumbing on the island seemed more in the bodging line than you might expect from all-conquering aristo-plumbers. The large tin sheds in which crashed cars were carefully dismembered to provide spares for those left behind to carry on their suicide missions, swerving around the potholes into the path of oncoming trucks, came to resemble cathedrals to the deity, Deceit. The posing riot police, imported for the day from a nearby island to keep tabs on the excesses to be expected from the Easter goat races, suddenly became more threatening than droll.

I was well on the way to spoiling my holiday. “No stains. No learning.”

Could it really conceal this monstrosity of ill-will? No religious meaning despite all the signs of a strong local religious sentiment. Doubts about the probability of right-thinking about the balance of education and skills, quarried from the stale leftovers of British colonialism. Dismissal of the idea of roguish plots as a brief moment of paranoia. What could it mean?

Having always driven by the sign, this time I parked the car. I took a closer look at the church and found no clue. I found another, opposite, in a plantation of bananas of the Moravian persuasion. Again no clue. I strolled past the school. Its lines of white-shirted, uniformed, boys and girls were as spick-and-span and attentive as any Chris Woodhead might wish to see. No sign of division into philosophers and rude mechanicals. I wandered on to the roti shop. I bought a vegetable roti, a wrap of unleavened bread surrounding a fragrant oozing mass of curried potatoes and chickpeas.

And the penny dropped. No stains. No learning. It’s an advert for washing powder. It’s guaranteed to keep schoolkids’ shirts and blouses white, however much real life intrudes into education.

David Sherlock is chief inspector of the adult learning inspectorate