A French anarchist, Martial Bourdin, accidentally set of a bomb that he was carrying through Greenwich Park at 4.45pm on 15 February 1894. An account of events by one of my ROG colleagues can be found here and a flavour of the media storm that the event provoked (which provided inspiration for Joseph Conrad's The Secret Agent) is given here. The image accompanying this post, and another fantastic image from the illustrated press here, show the public's fascination in the event. There has been much debate over what Bourdin's target actually was but, given that the "zigzag path" beneath the Observatory is not a main route, it would appear that the Observatory was the intended target. For nearly a decade Greenwich's local meridian had been designated the Prime Meridian for the world, and that the international day began at midnight in Greenwich - perhaps, then, what Greenwich stood for was indeed a tempting target for an anarchist.
The decision regarding the Prime Meridian was made at the International Meridian Conference held in Washington in 1884, the proceedings of which are available online. These show that the French delegates were far from happy about the idea of making Greenwich rather than Paris (or at least a 'neutral' position) home of the Prime Meridian.