Inchtuthil

It was built in AD 82 or 83 as the advance headquarters for the forces of governor Gnaeus Julius Agricola in his campaign against the Caledonian tribes. Positioned at the head of one of the main routes in and out of the Scottish Highlands, it was occupied by Legion XX Valeria Victrix and covered a total area of 21.5 hectares (53 acres).

Construction of the large fortress would have taken two or three seasons and a temporary camp was built nearby to house and protect the soldiers over the winter. Additional, smaller forts were built further north and south at the mouth of each nearby glen forming what are now referred to as the Glenblocker forts.

The fort at Inchtuthil is thought to be part of the Glenblocker forts, as well as others in Strathmore, such as Cardean and Stracathro, formed a uniform system composed of several elements, the forts and watchtowers on the Roman road of the Gask Ridge, the Glenblockers and the Strathmore forts. Inchtuthil as the largest military base would have functioned as the lynch-pin and the only site large enough to launch an invasion into the Highlands and beyond.

Layout and garrison

Unlike other legionary fortresses in Britain, Inchtuthil was not later built over and its layout was still largely preserved when Sir Ian Richmond excavated it between 1952 and 1965. It is therefore notable as the site which provides the only complete plan of a legionary fortress anywhere in the Roman empire. Its defences consisted of a turf rampart faced with stone, with an outside ditch and gatehouses on each side, following the standard Roman plan. The legion it accommodated would have numbered 5,400 at full strength, though there would have been additional specialist troops accompanying them.

Facilities included a hospital (valetudinarium) that covered 5,000 square metres (54,000 sq ft), a workshop covering 3,500 square metres (38,000 sq ft), and 64 barrack buildings. The timber walls of these buildings have been calculated to have had a total perimeter of 7 miles (11 km). A headquarters building containing an aedes where the legion's colours and images of the emperor would have been kept has also been identified in the insula in the centre of the fortress. However, it was much smaller than would be expected for a legionary fortress, and must have been of a temporary nature. The large empty insula to its east should have been the site for the Praetorium, the commander's house. However, no signs of building foundations for such a large structure were found though the site had been levelled and prepared.

Inchtuthil was only briefly occupied and was evacuated around summer AD 86 and certainly no later than early in AD 87. The reason for this was probably that Legio II Adiutrix had been called to Moesia from its base in Deva Victrix (Chester) to deal with a Dacian invasion in 86 and XX Valeria Victrix was obliged to move back south to take its place. However recent archaeology has cast some doubt on this, indicating that the fortress may have been in use for considerably longer than previously thought.