1666 was a year. The year after the Great Plague hit London. The year of the great fire of London. Samuel Pepys recorded the year 1666 in loving detail. Many saw apocalyptic elements in the fire and plague, especially based on the relationship of the year-number to 666, and its pan-digital nature in Roman Numerals.

In sixteen hundred and sixty-six
Old London burned like rotten sticks.

  - Nursery Rhyme