Iron Age surprise: Silbury Hill gets a young friend in the north - a large mound in Yorkshire

Written by Tony Millett on .

The Skipsea Castle mound (Photo from project website)The Skipsea Castle mound (Photo from project website)Dr Jim Leary investigated Silbury Hill in 2008 and three years later he led the team that proved that the Marlborough Mound was a Neolithic structure not a Norman one - so becoming known as 'Silbury's little sister'.  Now his team have found an Iron Age mound at Skipsea in east Yorkshire.

The Skipsea Castle mound is another Silbury-type mound and once again - like the Marlborough Mound - it had long been thought to be the base built by the Normans for a castle.  

The Skipsea Castle mound is 13 metres high against Silbury's 30 metres. Silbury Hill and the Marlborough Mound were built about 2,000 years before Skipsea.

It had always been presumed that the Normans had made the mound at Skipsea to raise their castle motte and its defensive bailey higher and give it a huge advantage over the enemy. 

Now it is clear that - like the Marlborough Mound - some of the Normans' castle architects recycled much older mounds to become instant and raised foundations for the castles they were so good at building.

The team’s discovery makes Skipsea Castle mound the largest Iron Age mound in Britain and among the largest in Europe.

(Graphic from the project website)(Graphic from the project website)  Coring at Skipsea Castle - in the rain (Photo from prtoject website)Coring at Skipsea Castle - in the rain (Photo from prtoject website)

The discovery is part of a major archaeological programme entitled "Extending histories: from mediaeval mottes to prehistoric round mounds" - known for short as the 'Round Mounds Project'.  

Funded by a grant from the Leverhulme Trust and carried out by a team of researchers from the University of Reading (led by Dr Leary) and the Scottish Universities Environmental Research Centre, researchers began with a list of a thousand mounds - which they whittled down to 50 possible mounds in areas of known Neolithic activity.  

They then reduced the list again to twenty feasible mounds. They investigated ten last year and are investigating ten more this year.  

This year's list includes Sherrington Castle in the Wylye Valley south-east of Warminster.  In September this hidden mound, which no longer has any obvious signs of its castle, was subjected to the team's prime investigative method  - their 'apple corer' technology.

This produces cores of soil through the mound to its base - in Sherrington's case this was just three-and-a-half metres of mound before they hit the base chalk level.  The core then goes back to the laboratory and is analysed in minute detail for items like seeds and pollen, insects and mollusc shell, which can be dated using radiocarbon techniques.

Members of the team - l to r Elaine Jamieson, Phil Stastney and Dr Jim Leary - with a core taken from the Sherrington Castle moundMembers of the team - l to r Elaine Jamieson, Phil Stastney and Dr Jim Leary - with a core taken from the Sherrington Castle mound

They are also using analytical earthwork surveys and detailed environmental reconstruction on each mound.  Along the way they are adding masses of knowledge about the mounds - even those which turn out not to be Neolithic.  For example at Sherrington they found evidence that the castle on the mound had a tower.

The Marlborough Mound - a listed monument in nthe College groundsThe Marlborough Mound - a listed monument in nthe College groundsThe Skipsea discovery is, says Dr Leary, their first major result: “To say that the discovery of an Iron Age monument hiding in plain sight was surprising is an understatement. Conventional wisdom has suggested that castle mottes were brought to England by the Normans, following the conquest that began in October 1066, exactly 950 years ago."

“Castle mottes exist up and down the country, but their huge size means they are rarely excavated and as a result much of what we previously thought we knew about their date was based on scant documentary evidence and guesswork."

“I excavated Silbury in Wiltshire in 2008, and now to discover the Silbury Hill of the North is wonderful. It adds so much more to our understanding of the people who lived in Britain 500 years before the Romans arrived.”

Mottes are earthen mounds that often had a wooden or stone tower constructed on them, and were sometimes coupled with a defensive enclosure known as a bailey.

There will have to be some swift re-writing of guidebooks: "Motte-and-bailey castles of this type are not rare, but Skipsea’s conical motte appears to be exceptionally large. In fact, this is an illusion created by its carefully chosen location on a natural glacial mound."

The Round Mounds Project's website is here.

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