I love a chippie dinner as much as the next person, but any shop I visit must follow some rules.

Firstly, the chips have to be thick and soft – no “triple-fried” or “shoestring” anything, and I’ve got to see grease splotches leaking through the paper bag.

Secondly, the people making my dinner must be okay with drowning my chips in vinegar (I’m THAT person).

I’ve always wondered why fish and chip shop vinegar seemed to satisfy me more than the stuff I have at home, but chalked it down to the mass of deep-fried joy it always comes with.

To my surprise, though, it turns out fish and chip shop “vinegar” isn’t the same thing as the bottle in my cupboard ― in fact, it’s often not “vinegar” at all.

It’s technically a “non-brewed condiment.”

Whereas vinegar is made using a two-step fermentation process (first alcohol is brewed, then oxygen is allowed to get at the booze to create acetic fermentation), “non-brewed condiment” is a mixture of water, ethanoic acid, colourings and flavourings.

It saves time and money as it doesn’t need to be “brewed”. When sold in bulk it can come as a concentrate, which chippies water down for consumption.

This “non-brewed condiment” is also halal, thanks to the lack of the tiny amount of alcohol vinegar uses, and it can sometimes be gluten-free which malt vinegar patently is not.

Due to the lack of brewing, the condiment can’t be sold as vinegar under UK law.

So the next time you order “salt and vinegar” chips from your local chippie, take the time to double-check the bottle if you want to be sure (though if, like me, you like the taste regardless, I recommend just rolling with it).

A long time, but it’s hard to work out exactly when the first bottle was made.

In a 1924 Parliamentary discussion, a Mr Hannon proposed a “Bill to prevent the sale of liquids or products made in imitation of and purporting to be vinegar.”

In other words, he was sick of seeing “non-brewed condiments” shilled as the real thing.

Mr Hannon pointed to a 1921 profiteering enquiry which looked into “the fact that brewed vinegar costs twice as [much] as unbrewed vinegar results in unbrewed vinegar being sold by dealers at a margin of profit much greater than that which is made on brewed vinegar”.

That means “non-brewed condiment” must have been around for at least 103 years ― and IMO, anything that sticks around that long has to be worth its salt (sorry).