Panther Westwinds had been established by fashion designer Robert Jankel to produce expensive and bespoke cars for the customer that wanted something entirely different.

Jankel began working on a car that would appeal to the Rolls-Royce owner looking to trade down to something more economic, yet still considered higher class — losing nothing in terms of luxury or build quality.

The Triumph Dolomite was selected for improvement, due in part to the vehicle's combination of advanced engines and upright driving position, which offered a blend of modern and traditional luxuries.

[1] The Rio was advertised as:"Combining characteristics combined in no other single car — the very highest level of luxury, appointments and smooth quietness with superb handling, a 115 mph (185 km/h) maximum speed, 0–60 mph acceleration in 8.7 seconds, the opulence of Connolly Leather, deep pile carpeting and burr walnut in the finest limousine traditions with the fuel economy and manoeuvrability of a compact family saloon; Panther coachbuilt quality and safety engineering with total functionalism; hand-crafted exclusivity without ostentation."

Problems for the Rio included the fact that the new thicker, fatter seats resulted in a more cramped interior than the Dolomite.