1983–1997: The District of Lisburn, and the District of Castlereagh ward of Carryduff. 1997–2010: The District of Lisburn wards of Ballinderry, Ballymacash, Ballymacbrennan, Ballymacoss, Blaris, Derryaghy, Dromara, Drumbo, Dunmurry, Glenavy, Harmony Hill, Hilden, Hillhall, Hillsborough, Knockmore, Lagan Valley, Lambeg, Lisnagarvey, Maghaberry, Magheralave, Maze, Moira, Old Warren, Seymour Hill, Tonagh, and Wallace Park, and the District of Banbridge wards of Dromore North, Dromore South, Gransha, and Quilly. 2010–present: The City of Lisburn wards of Ballinderry, Ballymacash, Ballymacbrennan, Ballymacoss, Blaris, Dromara, Drumbo, Harmony Hill, Hilden, Hillhall, Hillsborough, Knockmore, Lagan Valley, Lambeg, Lisnagarvey, Maghaberry, Magheralave, Maze, Moira, Old Warren, Seymour Hill, Tonagh, Wallace Park, and part of Derryaghy, and the District of Banbridge wards of Dromore North, Dromore South, Gransha, and Quilly. The seat was created in 1983, as part of an expansion of Northern Ireland's constituencies from 12 to 17, and was predominantly made up from parts of South Antrim and North Down. In their original proposals, in January 1980, the boundary commission proposed calling it 'Lagan'. In further revisions in 1995 it lost some areas to both Belfast West and Strangford. Currently the constituency contains most of Lisburn district and part of Banbridge district. Following their review of all parliamentary seats in Northern Ireland prior to the 2010 United Kingdom general election the Boundary Commission for Northern Ireland made alterations to Lagan Valley. In an unprecedented decision, passed by Parliament through the Northern Ireland Parliamentary Constituencies Order, one electoral ward was split between two constituencies. This followed concerns in Derryaghy about being moved into the neighbouring West Belfast seat.
History
For the history of the equivalent constituencies prior to 1950 please see Antrim and Down and from 1950 until 1983, please see South Antrim and North Down. The constituency is overwhelmingly unionist and traditionally had one of the highest votes for the Ulster Unionist Party in all of Northern Ireland, due in part to the personal popularity of Jim Molyneaux. Since his retirement in 1997 the seat has been represented by Jeffrey Donaldson, who many initially saw as the rising star of the UUP. However, Donaldson had a fractious relationship with the party, which at times was reflected in the election results. In the 1998 Assembly election he was controversially and publicly blocked from standing. In that election the UUP lost votes to many fringe unionist parties. In the 2001 general election the votes for the UUP, Democratic Unionist Party and Alliance Party of Northern Ireland all remained remarkably stable compared to significant shifts elsewhere in Northern Ireland. Then in the 2003 Assembly election Donaldson was allowed to stand, despite, at this point, having resigned the UUP whip at Westminster. The UUP had their best result in the election, in part due to no candidate from either the UK Unionist Party or Northern Ireland Unionist Party defending one of the seats won in 1998. Donaldson's fractious relations with the UUP continued and the following month, he, together with fellow assembly memberNorah Beare, left the party and joined the Democratic Unionist Party. In the 2005 general election he held his seat for his new party.
