I hope everyone remembered to set their clocks back one hour last night after British Summer Time ended. We are, of course, now on Greenwich Mean Time until 27 March 2011.
Coincidentally, I found myself in Greenwich today and, as pictured, stood on the Prime Meridian. These days, as well as a brass strip showing the line of 0 degrees longitude, there is also a green laser beam that shines into the night sky towards the O2 dome, which is visible for about 15 miles.
The Royal Observatory at Greenwich is well worth a visit and of particular interest are the time pieces on display of John Harrison, who solved the longitude problem (the basis of the Channel 4 drama "Longitude" in 2000).
"Oxford time" is 5 minutes later than GMT. I gather that the Great Tom Bell at Christ Church College is rung at 9:05 pm (9pm on Oxford time) every evening for this reason. However, I have to admit that I have never witnessed and confirmed this myself.