There are certain shapes that need no introduction. A dome of marshmallow, wrapped tight in foil the colour of an old teapot, silver and red catching the light from the biscuit tin. You know it before you've even read the word on the wrapper. It's a Tunnock's Teacake, and it has been sitting in Scottish cupboards, more or less unchanged, for almost seventy years.

Born out of rationing, not indulgence

The story starts further back than the teacake itself, in Uddingston, South Lanarkshire, where Thomas Tunnock bought a small baker's shop on Lorne Place in December 1890. For decades the business was exactly what you'd expect of a small-town bakery — bread, cakes, a tea room, vans trundling round Glasgow delivering fresh bakes to the door.

It was rationing, of all things, that changed the company's course. In the years after the war, sugar and fat shortages made fresh cakes a difficult business — they simply didn't keep. So the Tunnock family began looking for products with a longer shelf life instead. The Caramel Wafer arrived in 1952, and the Snowball, built on Italian meringue, followed soon after. Then in 1956, Thomas's grandson Boyd Tunnock — who had spent time researching how to get the mallow filling right — hand-piped meringue onto a biscuit base and coated the whole thing in milk chocolate. The teacake was born, not as a treat dreamed up in comfort, but as a practical answer to a shortage.

A biscuit with a genuine sense of humour about itself

It has barely changed since, and that's very much the point. Boyd Tunnock, later knighted for his decades of work in business and charity, kept the recipe close and the company independent, resisting buyout offers for years while the teacake quietly became a genuine piece of Scottish identity — as familiar, in its way, as tartan or shortbread.

It has also had a stranger life than most biscuits ever get. It's been sent up on a weather balloon to the edge of the stratosphere. It danced, six feet tall, at the opening ceremony of the Glasgow 2014 Commonwealth Games — after which Waitrose reportedly sold 62% more of them the following day. It has, more than once, been cleared for use on RAF flights, after altitude-chamber testing confirmed, somewhat reassuringly, that it does not explode under pressure. Not many national treasures have been through quite that much quality control.

Why we keep drawing things like this

None of that changes what the teacake actually is at the kitchen table: a familiar shape, unbothered by trends, that means exactly the same thing to whoever opens the tin. That's the same instinct behind our food and drink illustrations generally — drawing the packaging people already know by heart, because getting something exactly, recognisably right is its own kind of design achievement.

Our teacake design started from the wrapper itself, the way most of our best-loved pieces do — that unmistakable dome, the twist of red and silver foil. It now lives in two forms in the shop. The Tunnock's Teacake card has quietly become one of our best-loved designs, printed on FSC-certified 320gsm stock and blank inside — it turns out very few biscuits double as well as a birthday card. The giclée print is a different proposition: a limited edition of just 80, signed and numbered, printed in-house on museum-grade cotton rag paper, and very nearly sold out. Once the last of the edition goes, it's closed for good.

Some things earn their place through decades of quiet consistency rather than reinvention. The teacake is one of them. We're just glad to have drawn it.

— Jude