Aerial shot of the site looking north-west. Excavation pictures by Jim Rylett
Our crowded landscape has revealed more of the secrets beneath its surface recently, this time at Fiskerton in Lincolnshire. A scheme to improve flood defences in 2001 involved stripping off a layer of topsoil close to the River Witham.
A row of wooden posts began to emerge, looking suspiciously significant, even to the engineers' untrained eyes. Work was halted and a team of archaeologists called in.
Some of the posts prior to their extraction. These examples are still 3 to 4m long.
The process of excavation and the ancient treasures found at Fiskerton are the subject of a 'Meet the Ancestors Special' entitled 'Celtic Causeway' due to be shown on Wednesday March 27th on BBC2 at 9.00pm.
It was no great surprise to those in the know that the area had a story to tell. The Witham Shield, currently residing in The British Museum, was found in the river in 1826. Dated to 400-300 BC, and over a metre long, the decorative shield is a fine example of Iron Age workmanship and the La Tene artistic tradition.
The Witham Shield, now in the British Museum.
Over a hundred and fifty years later the dyke was being dredged when a series of posts was uncovered. The landowner's son then found an early to mid-Iron Age sword with his metal detector.
Naomi Field's 1981 excavation revealed the posts to be a causeway. Hundreds of artefacts were found - spears, ornaments and tools as well as part of a human skull with a fragment of sword lodged in it.
Twenty years on from that original dig Jim Rylett, the Head of Excavation for the 2001 project, describes working on the site as "possibly a chance in a lifetime opportunity... it's one of those big beacon sites, of international importance."
A trench looking east. The causeway is at centre, where horizontal photo scale is.
This time round there were even more treasures on offer. More sections of the wooden causeway were dug out, some of them containing posts several metres long, plus a complete spear, a currency bar, a sword, a dagger, some bronze fittings and the icing on the cake - two Iron Age boats.
The key to the Fiskerton site is the level of preservation of the artefacts. The land around the river is marshy peat - perfect for seeping around an object and cutting off all oxygen. No oxygen means little or no bacteria to eat away at organic material and cause disintegration. Hence the finds at Fiskerton are in remarkably good condition.
Dendrologists have dated the causeway to a period between 457/6 BC and 300 BC. It appears to have been repaired and added to every eighteen years or so during this period. The construction of such a walkway on such a scale would have been a real feat of engineering at that time.
The currency bar was found about forty metres upstream from the causeway and is puzzling, its exact purpose is unclear.
Rylett's theory is that despite the period being known as the Iron Age there wasn't actually that much iron around: "it seemed to be relatively prestigious."
"They would have needed around one hundred kilos of wood to produce one kilo of raw iron. Prior to money, perhaps the currency bar was a way of making iron into standard size ingots, like a primitive form of currency"
One of the most spectacular finds: a virtually complete iron agespear, probably the first such example found in this country. Iron spearheadis attached to an ash shaft, a thin dowel c. 0.01m diameter and c. 2m long.
Maisie Taylor, an archaeologist specialising in ancient wood, was involved in both the 1981 and the 2001 digs. She explains the significance of the spear, found with a complete shaft: "it's not unique to find fragments in sockets but this is nearly six feet long, as far as I know, in this country it's unique to find a spear with the shaft and both ends perfect."
The shaft is made from split ash, a wood known even two thousand years ago for its shock-absorbing and elastic properties.
In the second week of Rylett's excavations the first log boat was found. Unfortunately it had been disturbed at some point in the past, probably fifty or sixty years ago, which let in the dreaded air. Taylor describes its condition - 'none of the pieces was bigger than a dinner plate, it had the texture of a biscuit and couldn't support its own weight.'
Front half of logboat, with rounded bow furthest from camera. Stern extends beneath photographer as boat c. 7.2m long.
The disappointment didn't last long though, following the unearthing of a second boat, this time in immaculate condition. 'I don't usually get a boat in such a good position in controlled conditions. It's been very productive.'
The boat was apparently a votive deposit. It looks as if it had never been run on to a beach and was wedged into place with the back end actually pegged into place.
It's condition is surprising not only because of the preservation of the wood but also because it is an item of such high craftsmanship and value. This suggests that the site was a place of great importance to the people who placed the boat there.
Unpacking the wet timbers.
Upon careful removal from the dig site the boat was shipped down to the conservation experts in Portsmouth at The Mary Rose Trust.
With bags of experience under their belts after working on the Dover Bronze Age Boat as well as the Mary Rose itself, (among other projects) this is an interesting challenge for the team. Dr Mark Jones is leading the conservation project.
"It's a privilege to work on ancient objects, I get a great buzz from it, but at the end of the day we only have one chance to get things right."
Everything must be recorded in minute detail.
The first step was to identify the true condition of the wood. It arrived at the laboratory in twenty-six carefully packaged pieces. Core samples were taken for examination under the microscope to determine a course of treatment.
The timbers are actually very soft to the touch and require very gentle handling. They will all be immersed in treatment tanks in a solution of polyethylene glycol for twelve to eighteen months and then dried in one of two ways; either freeze drying, which would take up to six weeks or controlled air drying, which would take six months.
Fresh toolmarks are prominent on the timbers.
Once the drying is complete then the pieces will be re-assembled, a method of display devised, and they will take up residence in Lincoln City and County Museum along with the other Fiskerton finds.
The rest of the artefacts retrieved from the Fiskerton site are in the care of Rob White, Principal Keeper for the Lincolnshire County Council's Conservation Department.
He echoes his colleagues' feelings on the Fiskerton finds: "they are astonishing, a very special assemblage indeed - a challenge in conservation terms but also really rewarding. It's a marvellous group of items."
As with the boat, the items are undergoing careful stabilising, packaging and examination procedures in order to conserve them for the benefit both of the historical experts dying to get their hands on them and the museum-going public.
One thing that all of the finds now in Lincoln have in common is that they appear to have been deliberately broken or disabled in some way before being placed where they were found.
The dagger for instance was still sharp, yet the handle had been broken off. Archaeologists have come across this phenomenon before - at Peterborough's Flag Fen Bronze Age site for example.
This raises all sorts of questions. Were they offerings of some kind? Could this be another ritual landscape in the same vein as Stonehenge or the Norfolk beach where the Seahenge timber circle was found?
Who used the causeway? Why choose that particular area? Why did the causeway's sustained period of upkeep and repair come to an end?
This fascinating site has many stories to tell. The peat did a wonderful job of preserving its haul, now it's the turn of archaeologists, conservators and curators.
The Fiskerton finds will no doubt be the star of the show when Lincoln Museum opens its exhibition. While we wait as the artefacts prepare to face their public, the 'Meet The Ancestors' programme called 'Celtic Causeway' documents their emergence from their soggy hideaway. In the meantime, the Witham Shield can be seen at the British Museum.
The excavation was carried out by Pre-Construct Archaeology (Lincoln), and funded by the Environment Agency.
With thanks to Jim Rylett, Dr Mark Jones, Rob White and Maisie Taylor for their time and co-operation.