At the time the Underground was conceived, it was the bravest and most ambitious project in the world: a transport system that worked entirely below ground, out of sight of a city that even 160 years ago was congested and hectic. It shrunk the city to a manageable size. Little trains winding through tiny dark arteries, allowed inhabitants to get around cheaply and reasonably quickly. It was a democratizing force in London’s history. It provided shelter during the Blitz and even served as Winston Churchill’s makeshift office during WWII. It is an artery, an oddity and a curious piece of history.

The brand isn’t just a logo (known as the roundel); it is an entire visual system, which includes the ever-changing tube map, a typeface, a catch-phrase (“mind the gap”) and even distinctive station architecture.

As an exercise in design, the roundel is astonishingly simple and abstract: a bright red circle with a blue line through it. It is an example of a naïve brand that would probably never be designed in today’s relatively more sophisticated brand culture.

The logo began life as a simple way of marking stations. The font was born in 1916, created by Edward Johnston. The famous tube map was designed by Harry Beck in 1933 and was based on electrical wiring plans; it was a way of simplifying the ever-expanding system into simpler, more easily digestible shapes. For the newcomer, it serves as a baffling street map that has little to do with geographical reality.

The brand was never really designed as a whole concept in the conventional sense. Both the system and its brand identity evolved over time, from various ideas, changes and developments. The Underground started as separate and commercial train companies, competing for passengers with different overlapping, and often incompatible, infrastructure. Once the government purchased and amalgamated the separate systems, the logo and the signature map were commissioned and the brand began to take shape as a whole, becoming the Underground we know today. But both the system and the brand continue to evolve.

From a design point of view it is anthropologically fascinating to see the remnants of this evolution with different usage of the famous Johnston font, different ages and styles of the tube map in stations, and carefully preserved architecture from the 30s mingling with cutting edge 21st century station design.

The sheer scale of the system means that a total re-branding or restyling has never been completely possible; a subterranean trip across London allows you to piece together the tube’s design history through the odd fragments that remain. In terms of design, most brands are concerned with a few square inches on packaging or websites. The London Underground brand, on the other hand, physically covers 520 square miles.

London Underground’s brand is in a curious position. It is strong, well recognized and loved by many despite the fact that the system it represents offers little in terms of simple, comfortable and efficient service. Through past neglect, the Underground’s service is overpriced, over-complicated, inefficient, and fading at the edges. It is tolerated, if not despised by commuters who use it every day (in other words, regular customers) but loved by tourists and visitors. It is a strange case of “reverse brand loyalty.”

Globally recognized and steeped in tourist-friendly history and metropolitan character, the Tube’s tight links to history actually may hold it back from an innovative and exciting future. After all, when we think of the tube, many of us are reminded of singer Vera Lynn, wartime rationing, HP sauce, foggy London nights and the tube map. These are very strong images of a past era, and in a way, London Underground has done its best to capitalize on this image.

But now things are changing and while there is an enormous amount of work being done to modernize a rapidly decaying infrastructure before it falls in on commuters, the prospect of updating the brand image could prove to be a bigger challenge. No matter what developments are made to the service and the system, it is hard to imagine the tube ever shaking the echoes of its past and feeling new and efficient. Because of this, the brand’s strength is also its captive; it speaks more loudly of the early twentieth century than it does of the twenty-first, more historical oddity than rapid transit. How will London Underground make this rickety wartime brand into a modern, fast and efficient one?

Jackson Mahr is a director of Kodimedia, a London based design and brand consultancy.