Updated: New Anti-Dumping measure added.
Anti-Dumping Duty (ADD) is an import duty charged in addition to normal Customs Duty and is applied across the whole European Union (EU). It’s designed to allow the EU to take action against goods that are sold at less than their normal value – that being defined as the price for ‘like goods’ sold in the exporter’s home market.
You can find earlier ADD measures on the National Archives.
Source: HMRC