Historical information

William the Conqueror inherited Old Sarum from the last Saxon king of England. It was an ideal site for a royal castle. It was here in 1070 that William paid off his army after a long and bitter campaign in northern England. It was here in 1086 that he called together all the major landholders in England so they could swear allegiance to him. It was a crucial moment. The Domesday Book was being written, a threatened Viking invasion had only just been averted and William's eldest son was in armed rebellion. Old Sarum was an important place where this Norman king of England held power.
In 1794 the Ordnance Survey set out to check the accuracy of the first mapping of Southern England, which had begun ten years earlier. From a point just below Old Sarum Lieutenant William Mudge laid out a base-line 36,574 feet (11,253 metres) long. From each end of the line the positions of distant places were plotted using a huge theodolite made in 1791 by Jesse Ramsden. The accuracy of the process, which was repeated all over England, depended on Jesse Ramsden's craftsmanship and on William Mudge's surveying skill in setting out this first base-line from Old Sarum. The nearer end of Mudge's line is marked by an inscribed stone beside the modern A345 at Old Sarum.