What Car stipulate that the winner of the award "must have done more than anything else from the past 12 months to move things on".
Castle Bromwich-based Jaguar is a mere cottage industry alongside the mighty Audi, BMW and Mercedes-Benz. Yet its replacement for the retro styled S-Type was considered to have beaten the best the company's German rivals could offer.
This is even more of an achievement when set against the backdrop of uncertainty over Jaguar's future, with the sale of the company by owners Ford now imminent - most likely to Indian motor group Tata.
The magazine singled out in particular the way the XF out-drives the previously unbeatable BMW 5 Series, which is saying something, but also manages to be more supple on poor surfaces.
Accepting the award, Jaguar and Land Rover managing director Mike O'Driscoll said, 'This marks a very special day for Jaguar. We're back.'
Neither is What Car alone in praising the new Jag over its executive peers. In a three-way Auto Express group test against the Mercedes E280 CDI and BMW 525 M Sport, the 2.7 diesel version of the XF emerged triumphant.
Despite being the cheapest of the three, Auto Express described the car as "brilliant: superbly designed inside out, as well as fantastic to drive in all conditions and cost effective to buy and run. Jaguar should be immensely proud of its achievement."
"We're proud to say the XF is a British world-beater", the mag concluded.
But it's not just the Jaguar taking the honours. British-built stable-mate Land Rover won the top What Car award in the compact 4x4 category with its Freelander model, while the Discovery took the accolade for best large 4x4.
Al Kammerer, product development director Jaguar and Land Rover, pointed to strength in automotive manufacturing. 'The automotive industry in the West Midlands is alive and well,' he said.
In the hot hatch category, there was more success for British-built models with Oxford's MINI Cooper taking the title.