Complex sentence: 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 land border.
Split into simpler sentences: 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. Doing so would have meant patrolling a porous and meandering land border.