Marks Barfield cafe: One small, skinny mollusc please

The Bullring, Birmingham’s gargantuan consumer-fest, has spawned a minuscule bolt-hole where shoppers can pause for a few minutes to quaff coffee. This tiny stand-alone structure was created as one of the set-pieces of the complex by Marks Barfield Architects, the practice that envisioned the London Eye. Yet it is not a glitzy accessory to the retail developer’s standard wear that swaggers all around it. Still less is it a super-chic match for Future System’s curvy, silvery, sequinned Selfridges that rears up high just a few yards away.

Instead, thirsty shoppers are confronted with a maritime mollusc, crouched beneath a curving, scaly outer shell. The shell has an irregular, organic shape that spirals around mysteriously before your eyes as you encircle it. Even more organic and irregular is its outer surface of the scales, which come in random, swirling blotches of dark brown, bright orange, deep red, midnight blue and murky green, as if they covered a primeval creature in a swamp.

The shell turns out to be quite slender, hollow and open at both ends. One edge even cantilevers outwards and upwards from the pavement at a gravity-defying angle. The open shell invites passers-by to peer inside and right the way through, and from one angle it makes a perfect frame for gothic stone spire of St Martin’s church.

Inside, the carapace transmutes unexpectedly into a collection of regular, refined building components – just one vestige of the curving shell has penetrated the interior, and this erupts up out of the glass floor before folding over in submission in front of the serving counter.

Otherwise, the shell is lined in shiny profiled bronze. It is supported on eight curving steel ribs encased in polished stainless steel, each with a cord of fibre-optic light pulsating all along its underside. Its apparently open ends are in fact screened by clear frameless glazing. And, though not intended by Marks Barfield, Costa Coffee’s standard array of coffee bar furnishings completes the metamorphosis from invertebrate E E to city slicker.

Given the irregular, invertebrate form of the structure, it comes as a surprise to learn that it was inspired by a mathematical progression identified by the 13th-century Italian mathematician, Leonardo Fibonacci, and related to the golden section. “Illustrated graphically, Fibonacci’s sequence takes the form of a graceful spiral,” says Julia Barfield, partner of Marks Barfield. “It is a sequence found in natural patterns of growth throughout the universe, from sea shells and pine cones to the fractal patterns within galaxies. It is timeless and enduring.”

The tiny £1m shelter was constructed by Midlands contractor Thomas Vale under a design-and-build contract. Vale had to contend not only with the geometry of the golden spiral but with a site at the heart of Birmingham’s largest and most crowded shopping centre. It could, however, count on the assistance of the full design team, which was novated under the contract. The amphibious skin was made of thin copper panels, to which the curious blotching effect was applied on site using a cocktail of chemicals by patination specialist Capisco of east London.

Despite its glossy interior, it is the patterning and twisting form of the external shell that is the cafe’s main allure. It seems to emanate from a different planet than the rest of the Bullring. An alien creature within this commercial extravaganza, perhaps, but one that offers solace as well as sustenance to shoppers near their limit.