Early correspondence and papers, and miscellaneous records, are in HO 100 and HO 123 respectively. 'Six-figure' registered files of the Irish Office and Irish Branch are in HO 351, and other files of the Irish Branch in HO 348. Records of the Irish Constabulary are in HO 184 and of the Royal Irish Constabulary in HO 340. Correspondence and papers of the Imperial Secretary to the Governor of Northern Ireland are in HO 267