The three-year brief spans media relations, internal comms, publications, e-comms and on-location film management.
The Liberal Democrat authority received 60 expressions of interest for the work. After a four-strong shortlist was drawn up, only two applicants submitted a final pitch document - one of which was incomplete - allowing Westminster to clinch the deal.
Westminster first tendered for Richmond's brief over three years ago - one of the first attempts by a council to supply PR services for another borough - and has since handled its comms.
Richmond head of comms Cormac Smith said: ‘Our challenges will include lobbying for a better settlement grant from the Government, increasing revenue from filming, and raising our Audit Commission rating from "good" to "excellent".'
Movies that have been filmed in the borough include The Hours, Bridget Jones: The Edge of Reason and Finding Neverland.
The council made headlines last month with controversial proposals to penalise 4x4 drivers through higher parking charges.
Smith - supplied by Westminster - reports to Westminster head of marcoms Julia Corkey and Richmond head of policy Tracy Luck.
The responsibilities of Smith's team include the production of residents' magazine Arcadia and internal staff newsletter ‘Out of the Rut'. Its new account runs from January 2007 to January 2010.