Before the creation of the Irish Free State, British immigration law applied in Ireland as part of the United Kingdom. With the imminent prospect of Irish independence in 1922, the British Home Office was disinclined to impose passport and immigration controls between the Irish Free State and Northern Ireland, which would have meant patrolling a porous and meandering long land border. If, however, the pre-1922 situation were to be continued, the Irish immigration authorities would have to continue to enforce British immigration policy after independence. The Irish Department for Home Affairs was found to be receptive to continuing with the "status quo" and an informal agreement to this effect was reached in February 1923: each side would enforce the other's immigration decisions and the Irish authorities would be provided with a copy of Britain's suspect-codex (or 'Black Book') of any "personae non gratae" in the United Kingdom.