We gather the official position of the Prime Meridian at Greenwich is not to the liking of the powers that be at Google, as they have decided to shift it 100 metres or so east.
Yes indeed, according to the most reliable authority (The Greenwich Observatory press office - and if they don't know, who does?), the line marking zero degrees longitude passes right through the observatory buildings and across the forecourt where there is a lovely sculpture on top of which happy tourists can pose, one foot in the east and one in the west.
We'll leave it to readers to construct an eloborate conspiracy theory around the Google Earth Prime Meridian relocation outrage, which you can confirm here (.kmz file). ®
Thanks to Matthew Bednall for the heads-up on this one.