Metal detector users converged on a Lincolnshire field at the weekend in an effort to unearth the secrets of the past.

As part of an ongoing survey, around 20 detector enthusiasts were invited to trawl through mud on farmland at Fiskerton, near Lincoln.

The initiative was set up to help archaeological research into land which runs alongside the River Witham.

In the past 200 years the land has become a treasure trove of important finds – which has included iron age spearheads and tools.

Lincolnshire County Council archaeologist Adam Daubney said metal detectors play an important part in understanding our history.

“A lot of the really nice finds have been discovered since the 19th century but have not always been recorded accurately.

“When a metal detector gets a signal he will flag the location and dig for the object.

“Using GIS satellite technology we will plot the finds producing a map of the site.

“This will give us a better impression of the site and add to our historical research.”

For thousands of years the field would have been sporadically flooded as the River Witham ebbed and flowed.

Hundreds of artefacts are thought be hiding beneath the soil – as for centuries the Witham ferried trading ships to and from Lincoln.

Mr Daubney said it was important to locate the objects now. “The reason the Fiskerton site has preserved artefacts so well is due to the marshy peat that surrounds the river,” he said. “It’s 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.

“Now there is a dyke between the field and the river, which prevents flooding, but this is causing the land to dry out which could be destroying many important finds.”

One of the first artefacts to be found near the site was the Witham Shield – which was discovered in 1826 and dates back to 400-300 BC.

The decorative shield is over a metre long, is a fine example of Iron Age workmanship and is currently residing in the British Museum.

In 1981 an excavation revealed the posts of a Celtic causeway. Hundreds of artefacts were found including spears and ornaments as well as a human skull with a sword lodged in it.

And in 2001 more sections of the wooden causeway were dug out and archaeologists discovered two complete Iron Age boats.

Mr Daubney added: “This is an archaeologically important site and one of the few wetland sites in Europe which is under survey. Because the field is regularly ploughed this is a bit of a rescue operation.

“It will be interesting to look at the finds and see how quickly they are degrading.”

English Heritage is financing the dig and archeogical expert APS has been employed to help log the latest finds.

Metal detector expert Adge Winstanley (55), of East Barkwith, east of Lincoln, said: “The problem with scouring fen land is that any significant artefact is deep down.

“I will be hoping that there is a lot of stone on top of the soil – this is usually a good indicator objects are near the surface.”