There’s a certain soundtrack to the XJR575. It’s not just the threatening growl as the engine bares its teeth, or the low-down bawl evacuating the quad exhaust pipes. It’s not even your own squeals of joy as you mash the pedal, only to be pinned back against the seat by a fist of unholy torque.

It’s something more subtle, lurking in the background; the slow, inevitable tick-tock as Father Time counts down the lives of ludicrous luxury sports sedans like this one.

Those with a glass-half-empty worldview might start singing sad hymns and sending flowers to Jaguar HQ. The more upbeat, however, will want to praise the company for building an old-school, tarmac-guzzling fiend in a world now dancing to the tune of sparkly hybrid-electric tech and sanitised SUVs.

You know how most people eat with their eyes? At kerbside this car whets the appetite immediately, mainly due to its two feisty exclusive colours: Velocity Blue and the military-influenced Satin Corris Grey, a shade so tough – or over the top – Kim Jong-un probably decorates his bedroom with it. Gloss black 20-inch alloys, low air intakes and twin bonnet louvres add to the anticipation.

But the XJR575 doesn’t follow its theatrical opening salvo with an upper-cut, knocking the fun out of you. After the boisterous start – from zero to 100km/h in 4.4 seconds – the whole experience smoothes out somewhat as the Jaguar surges assuredly through the eight-speed automatic ZF ’box.

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Even so, the XJR575 is engaging and insanely fast on any type of road. In a straight-ish line on Portugal’s highways, even deep into the rev range there are never-ending pockets of power and torque waiting to be plundered – a fact borne out by the powerplant’s numbers: 423kW at 6250-6500rpm and 700Nm at 3500-4500pm, all channelled through the rear wheels only.

As befitting a premium sedan costing north of $300,000, the double-wishbone suspension smoothes out most bumps, even on Portugal’s gnarlier mountain tracks.

It was in these conditions that we expected the beefy Jag – 5.13-metres long, 1875kg – to show some glaring limitations. But it didn’t, by and large.

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Powering out of tight corners, the colossal 295mm-wide rear rubber continues to handle all that torque and the car remains surprisingly athletic yet firm for a big horizontal wardrobe. Electric rather than hydraulic steering now features on all rear-driven XJs, but feedback is still communicative, though if a touch heavy after prolonged periods of twisty hill work.

Long may it defy that slowly ticking clock.

Rating: 4 stars out of 5

2018 Jaguar XJR575 specs Engine: 5000cc V8, DOHC, 32v, s/c Power: 423kW @ 6250-6500rpm Torque: 700Nm @ 3500-4500rpm Weight: 1875kg 0-100km/h: 4.4sec (claim) Price: $306,475 Like: Blistering performance; great handling; meaty brakes Dislike: Wind noise; weighty steering; pricey options list