Gun End of Base?

If you live in the Salisbury area you will likely be familiar with the ancient site of Old Sarum. Old Sarum was originally an Iron Age hill fort, and following the Roman invasion of Great Britain it became the Roman settlement of Sorviodunum (43 AD – 410 AD). The site remained in use as a fortified settlement during the Saxon era and the Normans erected a motte and baily castle on the site (circa 1069).

A cathedral was built on the site between 1075 and 1092 and this was followed by the construction of a Royal Palace within the inner castle between 1130 – 1139. As the hill fort of Old Sarum was somewhat exposed to the elements, it was eventually decided to relocate the cathedral to a less exposed position, and in 1220 the construction of what would become New Sarum (Salisbury) Cathedral commenced. The general populous of Old Sarum followed the relocation of the cathedral, and Salisbury began to emerge as a settlement as the population moved themselves and their homes from Old Sarum. By 1240 the majority of the local population had abandoned Old Sarum in favour of Salisbury. Even though Old Sarum was now effectively population-less it still retained the right to send two members of parliament to the House of Commons. As such Old Sarum became known as one of the most famous “Rotten Boroughs” in the land, with wealthy people owning the land to ensure that they could become elected to parliament.

What most visitors to Old Sarum will miss however is a stone monument on the opposite side of the A345 to Old Sarum, which sits half way between Old Sarum and the Portway roundabout. The monument is marked on Ordnance Survey maps and on 1:25,000 scale maps and it is accompanied by the cryptic label “Gun End of Base”. The monument itself clearly explains its purpose and bears the following inscription  “In 1794 a line from this site to Beacon Hill was measured by Capt W Mudge of the Ordnance Survey as a base for the triangulation of Great Britain”.

It seems that in 1794 Captain William Mudge (1762 – 1820) of the Royal Artillery measured the distance between the site of the monument and nearby Beacon Hill, which is approximately 7 miles north east of Old Sarum and can be found between the A303 and the village of Bulford. This measurement apparently became the baseline from which the first definitive mapping survey of Great Britain began. The label “Gun End of Base” on today’s Ordnance Survey map apparently refers to the spot at which a cannon was buried vertically in the ground. It seems that the buried cannon would have been used as a point for Mudge to erect his theodolite on, prior to him making his measurements.

The question that springs to my mind is whether the label “Gun End of Base” appears on any other Ordnance Survey maps or if it is particular to Old Sarum. Time to get looking!

The monument to Captain William Mudge.

Old Sarum from a distance.

Information board showing an aerial view of Old Sarum.

Looking towards Old Sarum's motte.

The motte and its protective ditch.

Ruins inside the motte.

Looking out from the motte towards the ruins of the Old Sarum Cathedral.

New Sarum Cathedral can be seen in the distance.

A model showing what the motte may have once looked like.

Pictures, Wiltshire (August 2014).

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