Christopher Hirst: A square seen in the best circles

Forty years on, the After Eight continues to exert a strange power

Amid the welter of shocking headlines this week, one was particularly devastating in this season of indulgence: "After Eight factory to close." Does this mean the end for the "wafer-thin mint" that, along with Old Spice, Wills's Whiffs and Harvey's Bristol Cream, was an essential part of yuletide sophistication from the Seventies onwards? Has its role as chocolatey digestif been usurped by the ambassadorially endorsed Ferrero Rocher? Mercifully for those addicted to this slender treat, the answer is no.

Though Nestlé, which took over the brand from Rowntree in 1988, plans to close the After Eight plant in Castleford, West Yorkshire, it is switching production to its Halifax factory, the home of Quality Street. Far from going the way of lost brands such as Spangles, the Tiffin bar and Five Boys chocolate, After Eights are still very much with us. The Castleford plant makes one billion of them per year and more are produced in a Hamburg factory to satisfy continental cravings.

The potent appeal of After Eights goes way beyond confectionery. When the sweet first appeared in 1970, I remember the fascination induced by its evanescent slenderness. The scarcely there choccies tempted without sating. Of course, this only prompted repeated delving into the dark-green box. Mr Creosote was not the only one to find them irresistible. The resulting pile of little square envelopes was a tangible sign of their addictive quality. "Have you eaten that many?" my mother would exclaim.

Then there was the name. In an era when most people had their evening meal at 6pm (if not before), the brand hinted at risqué worldliness, fine dining and, just possibly, seduction. Early campaigns linked this mass market sweetie with Ferraris and Eaton Square. Elegant advertisements insisted that they were "squares seen in the best circles". This aspirational theme still continues on the confection's website, which suggests that "deep, existential conversations" will result from consuming After Eights to the accompaniment of Charles Aznavour and Edith Piaf.

If the adverts suggested that indulgence in the mints would transform us into James Bond, the real result of their calories and moreishness is more likely to be Billy Bunter. Though mint has "digestive properties", according to the Oxford Companion to Food, this element of After Eights is overwhelmed by the quite astonishing sweetness of the fondant filling. Initially, this is a stiff mixture of saccharose (table sugar), water and a small amount of an enzyme called invertase. The resulting rigidity allows the slender square of fondant to be enrobed with dark chocolate. But there is even more fiendish ingenuity to the After Eight. During three months maturing in the dark-green box, the invertase slowly breaks down the saccharose into the more soluble sugars fructose and glucose. The fondant centre becomes more liquid and the near-miracle of the After Eight is achieved.

Forty years on, the sweet continues to exert a strange power. In her bestselling book The Flavour Thesaurus, about "flavour combinations", Niki Segnit's consideration of the love affair between mint and dark chocolate is a paean to After Eights. It starts ecstatically ("you can feed it to me till my teeth ache") before turning weirdly mystical: "It was around Christmas of 1978 that I realised the potency of the After Eight mint as a symbol of infinity ..."

Some may suggest that these musings might be the consequence of an excessive indulgence in chocolate, fructose, glucose and invertase but there is no sign that Ms Segnit has reached satiation. Quite the reverse. She insists that the combination of chocolate and fondant in After Eights "seemed powerful arguments for never stopping eating [her italics]." She even imagines "smearing a hint of Rowntree's No 8 behind each ear" instead of perfume. How sophisticated can you get?