Original sentence: When Northern Ireland was created as a separate political entity in 1922, its system of local government was that previously established by the Local Government (Ireland) Act 1898 and this was not reformed until the current pattern of local government in Northern Ireland, with 26 councils, was established in 1973
Edited sentence: When Northern Ireland was created as a separate political entity in 1922, its system of local government was that previously established by the Local Government (Ireland) Act 1898 and this was not reformed until the current pattern of 26 councils was established in 1973