Boundary reviews
| Prior to 1832 | Since 1265, the Parliamentary County of Berkshire, along with all other English counties regardless of size or population, had elected 2 MPs (Knights of the Shire) to the House of Commons. The Parliamentary Boroughs of Reading, Wallingford and Windsor (formally known as New Windsor) had also each returned 2 MPs (burgesses) continuously since at least 1424. Abingdon (which was partly in Oxfordshire) had returned 1 MP since 1558 (one of only three single-member English Boroughs to do so). | |
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| 1832 | The Great Reform Act of 1832 radically changed the representation of the House of Commons. The county's representation was increased to 3 MPs, whilst that of Wallingford was reduced to 1 MP. | |
| 1868 | Under the Reform Act of 1867, the representation of Windsor was also reduced to 1 MP, at the same time expanding its boundaries to include Clewer and Eton (the latter being north of the River Thames in Buckinghamshire). [1] | |
| 1885 | Under the Redistribution of Seats Act 1885, [2] the county was divided into 3 single-member constituencies, namely the Northern or Abingdon Division, the Southern or Newbury Division and the Eastern or Wokingham Division. The Boroughs of Wallingford and Abingdon were abolished and absorbed into the county seat of Abingdon. Reading had its representation reduced to 1 MP. |  |
| 1918 | Under the Representation of the People Act 1918, [3] New Windsor was abolished as a Parliamentary Borough and replaced by the county Division of Windsor. Eton was now included in the Wycombe Division of Buckinghamshire. The Wokingham division was also abolished, with the majority of the seat, including Maidenhead being added to Windsor. The Municipal Borough of Wokingham itself was added to Newbury. Reading was expanded in line with the County Borough, including the absorption of Caversham, to the north of the River Thames, which had previously been part of the Henley Division of Oxfordshire. |  |
| 1950 | The Representation of the People Act 1948 [4] increased the county's representation from 4 to 6 MPs. Reading was split into the two constituencies of Reading North and Reading South. Wokingham was re-established, comprising the borough of Wokingham and rural areas to the south and east of Reading, transferred from Newbury, and extending eastwards to include the Rural District of Easthampstead (which incorporated Bracknell), transferred from Windsor. |  |
| 1955 | Under the First Periodic Review of Westminster Constituencies Reading North and Reading South were recombined, with one ward of the County Borough being included in each of the Newbury and Wokingham constituencies. |  |
| 1974 | Under the Second Periodic Review, [5] representation was increased back up to 6 MPs with the re-creation of Reading North and Reading South. The County Borough wards in Newbury and Wokingham were returned whilst Reading South was extended southwards to include parts of the Rural District of Wokingham, transferred from the constituency thereof. |  |
| 1983 | The Third Review [6] reflected the changes to the county of Berkshire resulting from the Local Government Act 1972 and saw major changes. The bulk of the area comprising the constituency of Abingdon had been moved to Oxfordshire, with the majority of its contents, including Wantage, Wallingford, Didcot and Faringdon, being included in the new constituency of Wantage. The town of Abingdon-on-Thames itself, together with areas to the west of Oxford, was included in the new constituency of Oxford West and Abingdon. The small part which was retained in Berkshire was transferred to Newbury. The county had absorbed the Municipal Borough of Slough and the small Urban District of Eton (which together had comprised the constituency of Eton and Slough) from Buckinghamshire. Slough was now formed as a new seat and Eton was added back to Windsor. A new constituency of East Berkshire was created, largely comprising the Borough of Bracknell (formerly the Rural District of Easthampstead), together with Old Windsor and Sunningdale, transferred from Windsor and Maidenhead. In addition, it included the parts of the former Rural District of Eton (including Datchet) which had also been transferred from Buckinghamshire to Berkshire and were previously part of the constituency of Beaconsfield. Reading North and Reading South were abolished once again and replaced by Reading East and Reading West. Reading East was formed largely from Reading South, but also included Caversham from Reading North. Reading West was formed largely from Reading North and extended westwards to include parts of Newbury. North-western parts of Reading South were transferred back to Wokingham. |  |
| 1997 | The Fourth Review [7] resulted in a further increase from 7 to 8 MPs with the abolition of Windsor and Maidenhead and the creation of the two separate seats of Maidenhead and Windsor. Maidenhead included Bisham and Cookham, and was extended westwards to include northern parts of Wokingham. Windsor included Bray, Eton and the Slough ward of Foxborough. It was extended southwards to include parts of East Berkshire (Datchet, Old Windsor, Sunningdale and Ascot). East Berkshire was abolished with remaining parts forming the basis of the new constituency of Bracknell, which also included the ward of Wokingham Without, transferred from Wokingham, and Finchampstead, transferred from Reading East. Reading East gained parts in the east of the borough from Wokingham in exchange for areas to the south, including Shinfield. It also gained the borough ward of Katesgrove from Reading West in exchange for the ward of Whitley. Newbury transferred two wards to Wokingham. |  |
| 2010 | The Fifth Review [8] saw only modest changes, including the transfer of Bray from Windsor to Maidenhead, Binfield from Bracknell to Windsor and the return of Foxborough ward from Windsor to Slough. There were further marginal changes due to revision of local authority wards. |  |
| 2024 | For the 2023 Periodic Review of Westminster constituencies, which redrew the constituency map ahead of the 2024 United Kingdom general election, the Boundary Commission for England opted to combine Berkshire with Hampshire and Surrey as a sub-region of the South East Region. As a result, Windsor now included Englefield Green and Virginia Water in the Surrey borough of Runnymede. The number of constituencies was increased from 8 to 9 with the creation of Earley and Woodley, which principally incorporated areas of Reading East (Woodley) and Wokingham (Earley and Shinfield) with small parts of Reading West and Maidenhead. To compensate Reading East (renamed Reading Central), three Reading Borough wards were transferred from Reading West. In turn, Reading West gained parts of Newbury and Wokingham, including the village of Burghfield, and was renamed Reading West and Mid Berkshire. Further changes included: |  |
