Although iron ore is common throughout Britain, there are very few iron production sites of Iron Age date in southern England, and the area must have been reliant on other areas for its metal. To release iron form its ore it has to be smelted – heated with large amounts of charcoal. The resulting red-hot metal was workable and could be hammered into ingots in the form of long bars, sometimes called ‘currency bars’.

Chemical analysis of the iron in these currency bars shows that they were often traded over great distances. As the iron itself was valuable, and perhaps more so in areas without smelting sites, it is probable that the bars were used in trade and exchange networks. Many of the hoards of currency bars have been found on the sites of hillforts, such as the one at Danebury Hill. Several different types of bar were found at Danebury hillfort, which may suggest that it was involved in trade and exchange with a number of communities. At Danebury evidence was also found of bars which had been cut up prior to being used to make iron objects, showing that they were not exclusively used as a type of currency but were also kept for practical purposes.