BBC Finds Coordinator: Yvette Staelens; "Some of the artefacts will decay significantly unless we introduce them to the correct storage environment. For example items made from metal." Metal items include a Roman coin made from a bronze alloy that is particularly susceptible to decay.
When the Romans invaded Druids kept 'The stone which the builders refused' Vault safe. Romans excavated Stonehenge center. Druids wise. Heelstone downplayed. Vatican letters (Roman) say J.C. claimed Mishkan beneath Stonehenge, counting Roman coins Sarsen numbers 51-60 excavated.