The French Revolution and the wars that followed in Europe in the late eighteenth century gave rise to the concern that France may invade Britain.
The Ordnance Survey was founded in 1791 to provide accurate maps of the country for the first time. Its first task was to map the south of England as this was nearest to France. Kent was surveyed first, then Essex. Within twenty years, around a third of England and Wales had been mapped at the one-inch to the mile scale.
In 1824, the Director-General of the Board of Ordnance was Major Thomas Colby. He was ordered to produce a detailed six-inch to the mile survey of Ireland. In the 1830s demands were made for a survey of England and Wales at the same scale. Norfolk was first surveyed between 1879 and 1886 at the six-inch to the mile scale.