On the hour, every hour

The Greenwich Time Signal has been a ubiquitous part of BBC Radio for a century, but few know what it really is and where it came from, says Rob Crossan

- Rob Crossan

ON September 17, 2008, anyone listening to the BBC's local and national radio stations could have been forgiven for thinking they had woken up in an alternate reality. Why? The most reliable noise in the world had just gone somewhat awry. The Greenwich Time Signal 'pips-those half-dozen high-pitched, strangely reassuring bursts of time-keeping precision noise-went horribly wrong that morning. Firstly, they were six seconds late; secondly, there was one pip too many.

This was a rare glitch in a system that for 100 years has been informing radio listeners across the globe exactly how to set their watches, when they should be leaving the house to catch a train or simply whether they should contemplate going to bed. It's a precious device and not one that the BBC is prone to using in other contexts lest confusion should be caused.