It may possess a highly advanced electric powertrain and an array of digital displays inside the cockpit but, in terms of handling, the Mirai unashamedly rolls back the years.

We don’t mean that as a criticism, either. It’s simply that the generous suspension travel and more relaxed approach to containing body roll and heave are reminiscent of the big European saloons of the immediate post-millennium era. The E39 5 Series comes to mind; not because the Mirai touts a subtly but sweetly tuned oversteer balance (it is much more understeer-prone than any BMW), or because the steering is especially transparent (though accurate, the EPAS rack has an oleaginous quality and is deathly uniform in its weighting), but because it can achieve that easy but accurate flow so many modern saloons have sacrificed in return for improved body control.

The Mirai will sporadically expunge itself of deionised water as needed. A button on the fascia clears the system before parking, if you'd rather it didn’t dribble on the floor

It has that detached elegance you’d expect from a boat-like Japanese executive saloon, with all the ease that goes with it, once you’ve acclimated to the dimensions. And we think this suits it well. Of course, the flip side is that the Mirai is not in any real way an enjoyable car to drive, beyond the very quietly satisfying act of keeping it adequately balanced on the throttle through corners and lazily flowing it down larger roads.

It never makes good on its rear-drive layout – it’s personality is too soft for that, and while pushing the car’s dynamics will reveal reasonable reserves of grip, the nose’s angle of attack remains steadfastly unresponsive to whatever the accelerator pedal is doing. Overall, this is a definite improvement over the Prius-based Mirai of 2014 but no dynamic alternative to the best-handling ICE saloons.

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Millbrook’s Hill Route isn’t the natural habitat for a mid- to senior-sized saloon with soft suspension and relatively little torque. With the same boat-like gait as the Honda Clarity FCV, the Toyota will tolerate being hustled but lacks precision in all areas, making it much less enjoyable or confidence-inspiring to plot along the barrier-lined bends of this course than, say, a BMW 7 Series or Mercedes E-Class.

However, to its credit, the Mirai never gets itself into any trouble. Its suspension might be supple but the car maintains good directional stability, and though outright grip levels are hardly exceptional, both ends of the car are consistent with one another, and the Mirai shows a mid-corner balance that yields higher speeds than you might be expecting.

Up the ante and you’ll spill into understeer, and only with the most assertive provocation can the Mirai be made to gently oversteer.

Comfort and isolation

Here we arrive at what is arguably the Mirai’s greatest strength: refinement. Clearly, with an electric powertrain, the noise generated by propulsive duties was always going to be negligible, and that’s absolutely the case.

At low speeds, the Mirai glides around with the serenity of larger premium battery-electric cars such as the Mercedes EQC or Jaguar I-Pace, if not quite summoning the anaesthetising qualities of something like a Mercedes S-Class. Occasionally you might detect a faintly electronic-sounding outburst from the direction of the front-mounted fuel cell unit, but progress is mostly a picture of calm.

Perhaps the slight busyness imparted by the 20in wheels fitted to our top-spec test car would give us reason enough to stick with the regular 19in alternatives, but in general the Mirai moves ever so deftly for something of its bulk. At higher speeds, the appealingly lazy ride quality is mostly unblemished, though sudden suspension inputs aren’t always dealt with especially neatly.

What owners will appreciate, however, is how quiet this loping saloon is on the move. At 70mph, our microphones registered just 66dB – as quiet as the £88,000 Audi E-tron S.