The Boundary Commission for England began reviewing constituencies in January 1946 using rules defined under the Representation of the People Act 1944, which excluded the City of London from the redistribution procedure;[4][5] the Commission recommended that the borough of Chelsea and the City of Westminster form a single Parliamentary Borough of Chelsea and Westminster with two divisions.

[6] In February 1948 the Government brought forward a new Representation of the People Bill which removed the right of owners of business premises to a second vote; this would have had the effect of reducing the electorate of the City of London from 12,500 to 4,600.

[8] In introducing the amendment the Home Secretary James Chuter Ede noted that the alterations to the constituencies in Westminster, Chelsea and Kensington had been agreed unanimously at a conference between the Members of Parliament and representatives of the boroughs affected.

[11] In initial proposals during the Third Periodical Review (1983), the Boundary Commission proposed to abolish the St Marylebone constituency and add four wards from it (Cavendish, Baker Street, Bryanston and Regents Park) to the previous City of London and Westminster South constituency; they provisionally named the result 'The City of London and Westminster'.

[12] For the Fourth Periodical Review (1995), the Boundary Commission paired the City of Westminster with the Royal Borough of Kensington and Chelsea for consideration.

In the latter, more residential, city it covers Westminster, Pimlico, Victoria, Belgravia, Knightsbridge, St. James's, Soho, most of Covent Garden, alongside parts of Fitzrovia, Marylebone, Edgware Road, Paddington and Bayswater.

In 1959, the boundaries changed, and the wards used instead were Abbey, Alderney, Aldwych, Berkeley, Cathedral, Churchill, Covent Garden, Dolphin, Eaton, Ebury, Grosvenor, Knightsbridge, Millbank, Regent Street, St. James's, Soho, Tachbrook, Victoria, Warwick and Wilton.

In 2002, a Local Government Boundary Commission for England review abolished the Baker Street, Belgrave, Bryanston, Cavendish, Knightsbridge, Millbank, St James's and Victoria wards.

The seat was expanded to bring the electorate within the permitted range by adding the Abbey Road and Regent's Park wards which were previously in the abolished constituency of Westminster North.

The seat includes iconic landmarks such as Buckingham Palace and St Paul's Cathedral, the West End's Theatreland and Soho.