Landowners have been warned the discovery of a valuable Roman helmet could trigger a flood of treasure hunters.

The find is the latest in a series of high profile artifacts unearthed by amateurs armed with metal detectors.

However the Country Land and Business Association is warning that property owners can become embroiled in costly legal disputes if they fail to agree contracts with anyone searching on their land.

There are an estimated 30,000 metal detectorists in Britain, they include Bill Wyman of the Rolling Stones....