On the face of it, one tin of antique cream emulsion paint would not seem offensive. Some may prefer magnolia, or brilliant white perhaps, but the item is basically harmless. No it isn’t, according to the Cardiff Bus company, applying the letter of new health and safety rules about public transport.

A driver refused to let Brian Heale, 73, an RAF veteran, buy his ticket and take his seat as he had a can of said paint with him. Only the intervention of a sympathetic café manager prevented the sad, ejected Mr Heale having to walk home in the rain for 20 minutes.

These rules ban guns, swords, gas cylinders and petrol from inside buses. This is not unreasonable. But there must be a distinction between, say, an Uzi or a Samurai weapon or a Molotov cocktail and a can of something with the Dulux dog on it, destined to be slapped — with the aid, possibly, of a dangerous roller — on kitchen walls.

It is not wholly clear whether the problem with paint is that it can be flammable or might emit foul fumes if exposed to other passengers. In either instance, it is classified as a “hazardous material” and is subject to regulation.

Not that it is prohibited entirely. To be fair, paint is permissible on a bus if it is, to quote the rules, “carried in two containers, ie, a sealed pot and a bag and is not left unattended on a parcel shelf where it could slide and tip, burst open and spread across the floor”.

Why paint would be that much less flammable for being inside a bag is not completely obvious. And if the “slide and tip” dictum is enforced rigorously, the days of placing heavy shopping on a parcel shelf are numbered. Someone inside officialdom has a tin ear. It is surely time to listen to common sense.