BALLISTIC performance, unique styling and a bolshie attitude mean the long-wheelbase XJ Supersport – the supercharged V8 flagship – is not for the faint-hearted, but there’s a sturdy (and disarming) undercurrent of quality, composure and technology that guarantees the Jaguar’s right to play in the rarefied performance-limo end of the new-car market. If you’re in the market for a Maserati Quattroporte or Mercedes-Benz S63 AMG, you ought to check out what the Brits are up to first, because the latest Jag flagship is quite a car.