If you stand outside the old Corn Exchange in Bristol, you'll see a clock with two minute hands above the entrance. One hand is set to London time, the other to Bristol's — ten minutes behind. The lag is because the sun reaches its peak over the second city a little bit after the first.
Of course, when it comes to scheduling anything with bounds beyond one city, having two poses an issue. This is why, in 1840, the British company Great Western Railway imposed what it called "Railway Time" across its whole network of trains, establishing Greenwich Mean Time as the first standardized time. And it's still the time zone used in the U.K. today. However, when several towns refused to adopt the time established by the Royal Observatory in Greenwich, the solution was to use two minute hands instead of one. And so the three-handed clock came to be.
