Following the partition of Ireland in 1922 some legislative and administrative powers were devolved upon the new Northern Ireland government, and others, called reserved matters, upon that of the United Kingdom. The reserved matters were the making of peace and war, armed services, foreign and dominion relations, elections to the United Kingdom parliament, dignities and titles, treason, aliens, naturalisation, trade and merchant shipping, wireless telegraphy, aerial navigation, coinage, trade marks, copyright and patents, postal services, customs and excise and income tax.
From December 1922 to April 1924 communication between the governments of the United Kingdom and Northern Ireland was maintained by the Irish Branch of the Home Office.
From 1922 there was also an office of the Imperial Secretary to the Governor of Northern Ireland, through whom business was channelled and who acted as adviser to the Governor on reserved matters.
The Imperial Secretary was S G Tallents, who had previously acted as Private Secretary to Lord FitzAlan-Howard of Derwent, the last Lord Lieutenant of Ireland.
The office was abolished in 1926.