Sensitive military details were once hidden from public Ordnance Survey maps for fear of invasion. This secret copy of an 1876 map of Dover was kept by the War Department in the 19th century. | British Library

This week we are celebrating 230 years of Ordnance Survey! Since 1791, Ordnance Survey has been mapping every inch of Great Britain producing maps, data and information which millions of customers depend on. From military maps helping to protect the nation to accurate location data relied on today by every one of us, innovation has always been at the centre of what we do. You can learn more about our journey from 1791 to 2021 here: http://ow.ly/VbKv50Fhu0J | Ordnance Survey