Revenue stamps of the United Kingdom
When Ireland was partitioned into Northern Ireland and Southern Ireland in 1921, separate revenue stamps were issued for both entities. Southern Ireland stamps saw little use since that political entity was quickly superseded by the Provisional Government of Ireland and later the Irish Free State (both of which applied overprints on various British and Irish revenue stamps). However, Northern Ireland continued to use separate revenue stamps until the 1980s. Northern Irish revenues include Civil Service, Dog Licence, Excise and National Insurance stamps, among many others.
Partition of Ireland
Following the start of the Troubles in Northern Ireland in 1969, the Sunningdale Agreement was signed by the Irish and British governments in 1973. This collapsed in May 1974 due to the Ulster Workers' Council strike, and the new British Prime Minister Harold Wilson considered a rapid withdrawal of the British Army and administration from Northern Ireland in 1974–75 as a serious policy option. The relevant cabinet notes remained secret until 2005.