Spelthorne was one of six hundreds of the historic county of Middlesex which covered its south west. It had thirteen historic parishes whereas the modern borough and seat has seven. The London Government Act 1963 placed the historic county in London except for two areas, one being the seven south-westernmost parishes of Spelthorne and Middlesex, placed since the commencement of the Act in April 1965 in Surrey.
The seat was created by the Representation of the People Act 1918 and amounted to the larger, slightly less built-up part of the increasingly outer metropolitan Uxbridge seat which was split, in 1918, in two. It was given county seat status for unimportant logistical purposes. It amounted to the obsolete hundred plus the small west-to-east parishes in the north of Harmondsworth, Harlington and Cranford as the seat took in seven late 19th century-formed areas of local government, including the Staines Rural District. Due to the incursion into Elthorne Hundred the seat could have more accurately been named South West Middlesex.
For the post-war 1945 election the seat lost an eastern section: three of the historic parishes namely Hampton, Hampton Wick and Teddington to the Twickenham seat (which shifted substantially south, shedding Labour-leaning Hounslow). The seat saw a northern exchange. It gained two small parishes (one of which, Yiewsley was of modern creation) to the NNW from its parent seat. It lost the similarly small Cranford and Harlington parishes to form, with parts of the parent seat, the new seat of Southall, which the incumbent for Spelthorne went on to represent in 1950.
In the 1955 redistribution Feltham became the southwest of the new Feltham seat. Since 1955 the seat has comprised the former urban districts of Staines and Sunbury-on-Thames, added in local government to Surrey in 1965, and merged in 1974 to form in local government the Borough of Spelthorne.
The seat was categorised as a borough constituency from the February 1974 general election and for that election unaffected in the periodic redistribution. In 1995 the small settlement of Poyle, transferred from Buckinghamshire to the area in 1974 and long part of the possessions of Stanwell in Middlesex, was transferred to the Borough of Slough.
The seat is south of Heathrow Airport bounded by a long meander of the Thames. It is a more built-up area with numerous but less expansive green spaces, fewer private roads and little woodland compared to further south in Surrey. Some 30% is embanked reservoir or low-lying flood plain therefore immune against building.[3] Contrasting with these large areas of fresh water, Surrey County Council have built a waste incinerator in Charlton in the seat and the 1970s saw the construction of the M3 and M25 motorways through the seat, the latter along its western border.
While relative to the county as a whole this borough is marginally less affluent, in national terms it is more affluent. Workless claimants (registered jobseekers) were in November 2012 significantly lower than the national average of 3.8%, at 2.0% of the population based on a statistical compilation by The Guardian,[4] only 0.3% higher than the affluent neighbouring constituency of Twickenham in London. Most residents can afford to buy their own homes: social housing accounts for only 10% of the total,[5] and the proportion of professionals and managerial workers is high. Spelthorne has Labour's highest vote share of the eleven seats (30.5%) in the modern reduced definition of Surrey, where Stanwell is as at 2024 the only County Council division (seat) held by a Labour councillor. Stanwell in common with Sunbury Common has significant social housing.
Spelthorne exceeds the average quota of commercial property of Surrey's seats — it contains about 20% of the county's commercial/industrial property, including large plants or wholesale units of Complete Cover Group, Kingston Technology, Edmundson Electrical, Esso Petroleum, Johnson & Johnson Vision Products, Thames Water, Shepperton Film Studios, wholesalers and storage companies. Major offices/creative facilities of BP (its global HQ), Del Monte, NatWest, Samsung, Richmond Film Services and film/television ancillary businesses are in the constituency.
The 1918 to 1945 broadest, initial version of the parliamentary division saw no marginal majorities and can be squarely analysed as a Conservativesafe seat based on length of party tenure and size of majorities.
Since the 1955 boundary reduction and a local emphasis or demand upon private housing relative to social housing, the reduced area has eight Conservative candidate majorities of greater than 11% and three lower majorities: 1966, 1997 and 2001. The earliest of these produced the narrowest margin of victory, 5% of the vote. Based on length of party tenure and majorities the seat would be considered safe by most UK electoral analysts including of academic standing.
The constituency's first MP was Philip Pilditch, an architect who piloted the Ancient Monuments Act 1931 through Parliament: see Scheduled Monument. The most recent MP for Spelthorne (prior to the 2024 election) was the former Chancellor, Kwasi Kwarteng (first elected in 2010).
Boundaries of Parliamentary Constituencies 1885-1972, compiled and edited by F.W.S. Craig (Parliamentary Reference Publications 1972)
Britain Votes 4: British Parliamentary Election Results 1983-1987, compiled and edited by F.W.S. Craig (Parliamentary Research Services 1988)
Britain Votes 5: British Parliamentary Election Results 1988-1992, compiled and edited by Colin Rallings and Michael Thrasher (Parliamentary Research Services/Dartmouth Publishing 1993)
British Parliamentary Election Results 1918-1949, compiled and edited by F.W.S. Craig (Macmillan Press, revised edition 1977)
British Parliamentary Election Results 1950-1973, compiled and edited by F.W.S. Craig (Parliamentary Research Services 1983).
British Parliamentary Election Results 1974-1983, compiled and edited by F.W.S. Craig (Parliamentary Research Services 1984)
Who's Who of British Members of Parliament, Volume III 1919-1945, edited by M. Stenton and S. Lees (Harvester Press 1979)
Who's Who of British Members of Parliament, Volume IV 1945-1979, edited by M. Stenton and S. Lees (Harvester Press 1981)