The 1920-30s was a time of tremendous innovation in metropolitan London, especially in the realm of public transport and urban design. This is when the clean lines of the Underground logo first emerged, when clear san serif fonts were used throughout, newly built stations designed along modernist lines, and -- in a real triumph of urban innovation -- Harry Beck designed the Tube Map diagramming the routes of the Underground in a simple but quite readable and usable fashion! Design impressario Edward Tufte recommends Ken Garland's history book, Mr Beck's Underground Map, and if you're curious about a quick graphic history of Tube maps, check out the London Tube Map Archive! Here's a more contemporary version of Beck's map... Beck's delightful map has been emulated around the world -- including here in Boston -- and is a great illustration of simplicity in design. Consider how much more difficult it would be to understand the actual geographic mess of the real transit systems in cities worldwide! FYI, the BBC4 did a nice video review of this Tube history which you used to be able to find on Smashing Telly, but it seems now down.