GM Europe, having decided in the 1970s that Vauxhall models would henceforth be engineered by Opel of Germany, put its plan into action initially with the Chevette (though it still had Viva running gear and engines) and then with the Cavalier, a car that shared almost everything with the Opel Ascona B except badging, trim and the ‘cat’s eyes’ front end. It even came out of the same factory. Eventually, the Cavalier did get UK production, and in 1981, with the Mk II model (Opel Ascona C), the GM strategy became clearer: in the UK, Vauxhall would be the main brand, and Opel would be phased out. As it turned out, no Opel equivalent of the Cavalier Mk II was sold in the UK, and Vauxhall and Opel dealerships were merged.
The Mk II Cavalier was not directly a twin: it included an estate model, which the Ascona did not have. The estate’s rear end in fact came from the related Holden Camira in Australia, and it was coupled with the rest of the car in the UK.
The Mk III, however, was pure Opel Vectra A. Vauxhall resisted the GM policy to go with the Vauxhall Vectra name in 1988, citing similarities with the unloved (by its end) Vauxhall Victor, though it relented in 1995 with the second generation of that model.