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Lloyd Bosworth : archaeologist | human | beard

Canterbury Roman helmet.

An incredibly well preserved bronze helmet, dated to the mid-1st century BCE Iron-Age, was found earlier this year near Canterbury by a metal detectorist who, thankfully, reported their find to Canterbury Archaeological Trust (CAT). CAT then carried out an excavation of the find spot to ensure that everything was fully recorded. Knowing that we have a high-resolution laser scanner at The University of Kent, CAT brought the helmet to us to see what this cutting edge technology would reveal.

A most important discovery

The helmet had been used as a cinerary urn and originally had a spike on the crown, also recovered by the detectorist, which had become detached due to corrosion. Within it were found many large pieces of cremated bone (currently with an osteoarchaeologist for analysis) and a well preserved copper-alloy brooch, which presumably held together a bag that contained the cremated bone.

With only one similar example coming to mind, that of a 1st century CE helmet from Poland, this truly is a unique find in Britain. A possible reason for the scarcity of this type of burial could be that military equipment did not belong to the soldier, and if they were killed, their equipment would normally have been returned to the quartermaster and reissued to another soldier. Another possible reason why this type of object was not used could be that bronze was a valuable metal, and often melted down and recycled to make other objects.

The Julius Caesar connection

The brooch from the burial has been dated to between circa 90 and 50 BCE, and the helmet is of a style widely used around the mid-1st century BCE. These dates are important when you consider that the upstart general, Julius Caesar, was waging his Gallic War during this period and that he invaded Britain twice in the middle of the 1st century BCE.

Is this the burial of one of Caesar’s soldiers killed during an ambush by the Cantiaci? Are we indeed looking at the first piece of archaeological evidence for Caesar’s invasions of Britain? Possibly. Or, possibly not. Very little in archaeology is as clear cut as ‘yes’ or ‘no’, despite what TV programmes have us believe. It is true that Caesar had Gallic soldiers fighting for him, and they would have worn helmets of this design. But it’s also true that Caesar’s enemies wore helmets of the same design. Many other narratives can be added to the above, but before any certainty can be claimed, much more contextual evidence is needed, as this helmet on its own is not enough.

Laser scanning

The helmet was brought to us in its excavated condition, meaning that only loose soil had been removed, leaving many areas of corrosion and compacted soil. Not a perfect surface to scan, but one that nevertheless revealed some hitherto unnoticed detail.

Laser scanning the Roman helmet with a Romer Absolute Arm.

Laser scanning the Roman helmet with a Romer Absolute Arm.

Close up of the Romer Absolute Arm laser scanner and helmet.

Close up of the Romer Absolute Arm laser scanner and helmet.

Laser scan of the right side of the helmet. The ‘peak’ on the left is actually a neck guard and is at the rear of the helmet.

Laser scan of the right side of the helmet. The ‘peak’ on the left is actually a neck guard and is at the rear of the helmet.

There are several factors that can cause problems when examining objects with the naked eye that the laser scanner can help reduce, or even eliminate. One is that of colour and texture variation, which can camouflage changes in surface detail. With the uniform colour of the scan data, this distracting effect is removed. Also with scan data, you have the ability to position a light source (or many light sources) in an infinite variety of positions. Sure, this can be done with the real world object, but not without repeated handling and moving, with the increased risk of damaging the object that this entails.

The laser scanner on our ROMER Absolute Arm has a resolution better than 0.08mm, and it can be seen in the images above and below that this is more than enough to pick out the indented decoration around the lower edge of the helmet. What can also be clearly seen in both images, but more so in the second, are indentations from hammer strikes made during the construction of the helmet, where a single sheet of bronze would be beaten into a former to create the helmet.

Laser scan data of the crown of the helmet. Hammer indentations from the manufacturing process can be seen to the left of the image.

Laser scan data of the crown of the helmet. Hammer indentations from the manufacturing process can be seen to the left of the image.

Another effect of this construction process can be seen in the thickness of the bronze and how much it varies across the whole helmet. This process of hammering the bronze sheet into shape would stretch the bronze ever thinner towards the centre of the crown. Here are some quick measurements from the scan data:

  • 4.372mm – rim edge
  • 1.427mm – neck guard thickness
  • 0.697mm – halfway up the back
  • 0.454mm – on the crown
  • 0.592mm – halfway up the front

Considering that this is the only protection for the soldier’s head, possibly save for a padded leather cap worn underneath the helmet, it’s hard to imagine that any blow to the head wouldn’t result in injury, let alone being harmlessly deflected.

The future

The helmet is now at the British Museum where it will receive minor conservation treatment while a specialist report is prepared for the coroner. After this there’ll be an inquest to determine whether or not it is treasure, followed by a valuation. As there have only been three other helmets of this period found in Britain to date, (only one of which is in a better state of preservation), it would be expected to command a high price on the open market. Add to this the potential connection to Caesar’s Gallic War and his invasion of Britain in the mid-1st century BCE, and the value could go through the roof. Let’s hope that whatever happens, the helmet gets to stay in Canterbury.

Press releases

The helmet in the news

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