The clock here is known as the Shepard’s Gate Clock and it resides at the Royal Greenwich Observatory in Greenwich, London. Those of you familiar with time will no doubt recognize the Royal Greenwich Observatory as the center of the time-keeping world. Or at least, it used to be.
This clock is actually a slave clock to the master clock located in the observatory. However, it is significant in that it is quite possibly the first clock to display Greenwich Mean Time to the public. That same time was transmitted to other clocks around the observatory, as well as to the London Bridge where a repeater send the signal to clocks around England. It helped to unify timekeeping in Great Britain, something that was important since the creation of the railway.
So, in a very real way, this is the public face of the clock that rules them all.
[Image Credit: Alvesgaspar]