Point of Interest Dossier: Nelson's ColumnCopy Anchor Link

"Then he thought of a complete stranger he had been standing behind in the queue at the supermarket two days before and felt a sudden stab — the supermarket was gone, everyone in it was gone. Nelson's Column had gone! Nelson's Column had gone and there would be no outcry, because there was no one left to make an outcry. From now on Nelson's Column only existed in his mind. England only existed in his mind — his mind, stuck here in this dank smelly steel-lined spaceship."

— The Hitchhiker's Guide to the Galaxy, Chapter 6

Nelson's Column was a towering granite monument in Trafalgar Square, London, on planet Earth. Following the vaporization of Earth by Prostetnic Vogon Jeltz and the Vogon Constructor Fleet, the monument became the focal point of Arthur Dent's psychological reckoning with the loss of his homeworld.

The Supermarket Queue & The Disappearance of EnglandCopy Anchor Link

When the Vogon flagship completed its jump through hyperspace to Barnard's Star—leaving Arthur six light-years from the place that Earth would have been if it still existed—Arthur discovered that his imagination could not initially feel the impact of the whole Earth having gone because the concept was simply too big:

1. Failure of Large Abstractions: Prodding his feelings by thinking that his parents and his sister had gone, or thinking of all the people he had been close to, produced no reaction at all.
2. The Supermarket Stranger & Nelson's Column: Only when he thought of a complete stranger he had been standing behind in the queue at the supermarket two days before did he feel a sudden stab: the supermarket was gone, and everyone in it was gone. Immediately afterward came the realization: Nelson's Column had gone! Worse still, there would be no public outcry over the loss of Nelson's Column, because there was no one left to make an outcry.
3. Existence Confined to Memory: Realizing that from now on Nelson's Column and England itself only existed inside his own mind—stuck inside a dank, smelly, steel-lined Vogon spaceship—closed a wave of claustrophobia around Arthur. Having grasped England's disappearance through Nelson's Column, he tested America and New York (which produced no reaction, as he had never seriously believed New York existed anyway), felt a slight tremor that the dollar had sunk for ever, suffered a nasty knock realizing every Bogart movie had been wiped, and finally passed out upon realizing there was no longer any such thing as a McDonald's hamburger, waking a second later sobbing for his mother.