Dissemination of absolute time in the United Kingdom

The description `absolute time´ is a shorthand expression for the labelling of events by reference to secular, running, timescales in an unambiguous and traceable way. Most practical timescales use trains of regular 1-second pulses traceable to hardware equipment, typically a caesium clock. The paper considers access to such timescales, which in turn, after a period of retrospect, can be traced to the international computed timescale Coordinated Universal Time (UTC), and discusses how closely they are likely to have agreed with UTC at the time a given observation was made. In short, it discusses how accurately one can expect to access UTC, `on demand´, and how accurately in `real time´: over, say, a few seconds. It also considers how the world UTC timescale is compiled, how it is implemented and disseminated in the UK, and the benefits brought by the new satellite navigation systems