ɪn nˈaɪntiːnhˈʌndɹɪd ˈeɪɾi tˈuː ðə bˈaʊndɚɹi ʌvðə ɹˈiːdʒən wʌz ɐdʒˈʌstᵻd wɛn pˈɑːɹt ʌvðə sˈɪɾi ʌv wˈɛstmɪnstɚ wʌz ɹᵻsˈiːvd fɹʌm ɪnðə nˈɔːɹθ wˈɛst tˈɛmz ɹˈiːdʒən.
In 1982 the boundary of the region was adjusted when part of the City of Westminster was received from in the North West Thames Region.