Ironically, at the same time as Baker was undertaking his privately financed survey of Cambridgeshire, a separate team from the government-funded Ordnance Survey was working on exactly the same task. Although its origins go back further, the formal foundation date of the Ordnance Survey - Great Britain’s national mapping agency - is usually taken to be 1791, when the Board of Ordnance, with the sanction of King George III, authorised the triangulation of Great Britain. Driven by fears of French invasion, the subsequent production of maps by the Board of Ordnance quickly turned the Government into a major map publisher.

Baker offered to sell his map of Cambridgeshire to the Board, but had to content himself with an undertaking that publication of the rival Ordnance Survey map (illustrated here) would be delayed. It eventually appeared in 1836.

The early days of the Ordnance Survey were marked by disputes about the most appropriate scales at which maps should be surveyed and published - the ‘Battle of the Scales’ as it was called. This was resolved in 1858, when a Royal Commission recommended scales of 1:2,500 for cultivated rural areas, 1:500 for towns and 6 inches to the mile and 1 inch to the mile for national mapping. Each county was mapped separately at the 1:2,500 and 6 inch scales, giving rise to the ‘County Series’ maps. The exhibition features the index for the six inch County Series maps of Cambridgeshire, the initial survey for which took place between 1876 and 1886.

After the First World War the resources available to Ordnance Survey declined whilst the demands being made upon it increased. In 1935 an investigative committee under the chairmanship of Sir John Davidson was set up to consider how the effectiveness of the Survey could be restored. One of the more significant recommendations of the Davidson Committee was that a metric National Grid should be adopted by Ordnance Survey maps to provide a reference system for the whole country. Since then there has been a progressive move towards the use of metric scales, with the old one inch maps being replaced by the 1:50,000 Landranger series (completed in 1987) and the six inch by 1:10,000 (completed in 1990). More significant still has been the move away from conventionally printed paper maps and into the world of digital databases and on-demand printing.