For those of you outside the UK, the Ordnance Survey is the official mapping provider in England, Scotland, and Wales. (There are separate providers for Northern Ireland and Republic of Ireland). The Wikipedia entry gives a summary of its history which officially started in 1791 as a response to the Napoleonic Wars, although there are precursors in the military surveys carried out in Scotland after the failed Jacobite rising of 1745.
When I was growing up in London my father ran a business maintaining RAF airfields in the south of England, this entailed a lot of travelling to oversee the work. He had a Standard Vanguard (I have the receipt for its purchase), roughly the equivalent of an Audi in today’s terms. He used to bring me back Ordnance Survey maps of the places he had been to, which I still have, so I learned how to read them from about the age of about five upwards. A lot has changed since then! There is a vast online resource of maps now, and if you look at the Geograph website I referred to in my last post you will see at the bottom of the page “More links for this image” which has a range of references which can keep you entertained for hours.