This super sedan had to change to conform to the times. Electric brings out a new degree of good, but it’s still fabulously bad.

Price: $254,600 as tested.

Powertrain: 4395cc V8 with electric motor, 535kW/1000Nm, eight speed auto, all-wheel-drive with 2wd option.

How big: 5096mm long; 1970mm wide; 1510mm tall.

We like: Still has that full out ‘driver’s car’ feel; can actually be economical (for an M5); looks fantastic; a technical titan.

Not so much: Engine sounds a bit flat; high-fuss paint finish; right at edge of complexity now.

VEE eight petrol: Thunderous, thumping thrust … but not great for thrift and, in respect to emissions? Don’t even go there.

Electric. Power aplenty, cheap to source, but lacking soul. Plus, the harder you go, the faster it depletes. If that’s your driving style, even biggest batteries struggle to meet demand.

For 40 years - since the original ‘E28’ version was launched using the 3.5-litre straight-six engine from the BMW M1 - the M5 has ruled of the high-performance sedan world drawing energy from petrol alone.

It cannot afford to any longer. Ultimately, it will eschew it entirely and go fully electric, perhaps as a hyperactive i5, perhaps as its own bespoke thing. One day.

In the here and now, it is changed considerably, but with compromise to what it believes will be acceptable to customers of a car that has gained a cult following thanks to its power, noise and desirability.

For now, therefore, a foot in both camps. Keeping the serious petrol engine and adding serious electric involvement, with plug-in recharging, is a new turn for BMW’s mightiest car-based M product.

While logical given the circumstances of the global motoring environment and potentially not as client allegiance risky as AMG has gone with the C63, in that it still has eight cylinders under the bonnet, rather than four, this is still a highly controversial concept.

Those who think this is ‘M’ for ‘madness’ are blind to world-changing realities. Sure, they can go on living in the past, but there is no refuge there. Their arguments carry no weight and are foolish. Literally, it’s time to plug on.

In as much as this powertrain is here because it has to be, it inhabits a car that continues very much as it always has … on its own terms, setting its own rules, laying down its own (not mis-spelled) ‘supercar in a sedan body’ lore.

What’s it like? Still breathtakingly brutal. As much as this new seventh-generation G90 version lays down a modern twist, it’s really just tipping a wink at notions of eco awareness.

Yes, it has a dual personality in that it can run up to 69 kilometres on electric alone. Yet there’s no doubt the primary point of the electric assistance is to make it even faster, more accelerative, more stomping than before.

It feels stupendous. Moreso here than it does in the other application it has in this market, with the super flamboyant XM Label Red. Even though the outputs are identical and kerb weights not that far apart, either, the M5 felt as though it would simply knock the SUV flat on its back.

Give this thing a boot and it blurs horizons and threatens to rumple road surfaces. If not for four-wheel-drive, you wonder it would be containable for daily road use.

What else? It’s said to be less thirsty. Probably is. When driven with sensibility, though even then the set-up is such that you still sense the latent power at easy call. That’s why it’s an M5.

Still, BMW can hand on heart say the M5 is capable of retuning 1.7 litres per 100km fuel consumption. The smaller print with this figure from the official WLTP test is that to even stand any chance of seeing it means keeping its battery topped up all the time and adhering very strictly to the testing protocol. Not likely? In which case, the more relevant count might be the depleted battery consumption figure, of 10.3 litres per 100km.

I saw something near that. Until the day I threw caution to the wind and gave it a decent run. At that point, it went back to old historic habit, with instant results in the 20s. Well, it’s an M5.

But there are ways and means to run it without draining the tank, to point driving it for reasonable distance at relevant speeds in pure electric was always possible during the whole week of test. It all comes down to how well you acquaint yourself with the car’s operating options.

About that. As simple as it is to set up shortcuts to allow it to be either an angel or a demon at press of a button, it’s still a highly complex car, so demands careful thinking about which modes are best suited. There are many permutations.

It was a pity that the very week I had it for test was just when Mike Eady, who in his capacity as the country’s only M-accredited driving instructor has enjoyed hands-on extreme driving of this car, to the Middle East for a brand event. Had he stayed local, I’d have likely been ringing him on a daily basis for ‘what about this?’ tips. He only escaped that because of the time difference.

As said, I’d driven this powertrain before, but in a hostile setting. Everything about the M5 simply reinforces that anyone buying into that XM Red is just so flush with silly money they’ve lost their commonsense. Or any sense of dignity.

It’s hard to argue sensibility with cars of this calibre but, all the same, it’s much less nutty to go to that uber XM with which it shares this powertrain, albeit for - gasp - $100k more than the quarter of a mill sought for this sedan.

Looks-wise, the M5 is as dedicated to embodying the ethos of abject brutalism, but overall the execution is much easier on the eye. It’s obviously a hotted-up version of the brand’s regular 5-Series/i5, but nonetheless exudes as something far more special; a precise and involving weapon.

The cabin expresses the performance-associated thematic. There’s a red engine stop-start button, and BMW M Sport red, blue and purple flashes everywhere you look from the touchscreen to the fabric of the seatbelts to the little illuminated logos in the backs of front bucket seats, which are brilliantly form-fitting and thankfully lacking the annoying carbon-fibre codpiece favoured for the M4/ M3 bucket seats.

The chairs, the door cards and, of course, the mandatory 12-o’clock marker at the apex of the flat-bottomed steering wheel are in red. Being an M it also gets carbon-fibre galore.

The cabin proper is roomy and comfortable; anyone brave enough to ride along in this rocket will find decent head and legroom in the back. Overall quality is extremely good.

The big feature is of course that massive, curved twin-screen digital layout atop the dashboard - 12.3 inches for the instrument display, and 14.9 inches for the infotainment screen. A click-wheel ‘iDrive’ controller makes the main display a touch easier to use when you’re on the move and find stabbing at a screen is hitting the wrong prompts. If you are working from the heavily-loaded app menu page, there’s every chance of that happening on a bumpy road.

The car’s M-ness in respect to operability means it has paddle shifters in carbon fibre, M1 and M2 memory buttons on the steering wheels and buttons on the centre console that trigger Road, Sport and Race modes - the first two okay for public environments, the latter really not.

Fiddling with the driving modes also changes the suspension firmness, the steering weight, the throttle response, and whether you want extra snappy responses from the eight-speed automatic gearbox. on top of this, you can sort the instruments in multiple ways, all with M-specific graphics and details.

I also set up the memory buttons for two extremes of operability; the first was basically tailored toward as extreme performance as I dared - so, basically, a lot of settings in Sport and Sport Plus - and the latter was for relaxed Hybrid-rich driving mode, which of course is the new territory.

As new as an M5 with ability to run wholly in electric is, even when it’s pulling fully or mainly from the battery, it still feels brisker than any everyday EV. The only commonality is that it’s totally quiet.

I found I could escape our sub-division wholly in electric mode and then involve the engine having turned onto, and come up to pace on, the 100kmh sector our little lane feeds into.

You’d wonder if this might be a bit of a stress for the engine, not least given this would be a engagement coming at start of day, but BMW’s engineers have clearly thought about that and refined the drivetrain accordingly so that the engine isn’t rudely awakened from dormancy. Even then the engagement is pretty seamless; you’re more aware of the engine’s background roar as it awakens than any jolting or so on as two become one. Once the engine warm, it’s even smoother.

The engineering is pretty amazing, really. Another neat tweak is that it’ll pre-position in a gear to allow it to deliver a punch of 450Nm of torque for brief periods, if that’s all you want.

You can also charge the 18.6kWh battery pack as you drive. That’s how I decided to have it, having found home charging was impossible, as the only cable provided for this demands a bespoke type two wallbox; no three-pin plug here.

Through a genuine oversight, the car came to me with the drive battery in such a low state of charge it opted out of engagement; that was sorted with a dealership visit next day, but because the car can only charge at up to 7kW on AC power, and with no DC fast-charging option, it took just over three hours to replenish, with progress being monitored on the ‘My BMW’ I have on my phone. Fine for overnighting, but having no way to quick-charge it when on a longer journey is a bit of a drawback that might weigh heavily on some.

Speaking of kilos … well, that’s been the elephant in the room. Electric doesn’t come lightly, pure and simple.

In briefing for the M5, M boss Franciscus van Meel admitted a multitude of options were considered - including smaller engines with less cylinders and a non-plug-in hybrid system - before concluding that the V8 was integral to the appeal of the car and that a useful electric range was desirable in Europe especially.

The challenge was then to make the hybrid system powerful enough, and the chassis of the M5 competent enough, to overcome the significant weight gain of a plug-in hybrid system - some 500kg.

The car’s mass is significant. It presses those 285/40 20-inch front and 295/40 21-inch rear tyres into the tarmac at a hefty rate of 2510kg. That’s full-on SUV count for a four-door sedan, whose heritage has been built on not just massive kapow but also scalpel-sharp handling and precision.

Conceivably, that’s why it has so much wallop: More than you might think. Yes, the twin-turbocharged V8 makes less on its own in this marriage than it dod when working in bachelorhood in the old M5; but that’s just the engine power. The electric side involves a 145kW motor, so together, they produce around 542kW, which is more than even the mighty CS.

Still, there’s fair heft to haul so the good side to it all is that the car carries it really well. Yes, there are occasions when you aware of it being a giant paperweight, but it’s a far better thing than the heavier-again XM, which really felt ponderous and detached.

The M5, by comparison, is highly intuitive and, if not utterly light-footed, feels fleet and lithe. That’s on some favourite country roads; it might be more pressed to pass itself off as a uber-athlete on a circuit. But, from my experience, the mass is only really noticeable when braking hard and, even then, the car keeps very good balance and turn-in.

The potency is certainly there; give it a bootful and keep your foot in it and it’ll be a challenge for your brain to keep up with the performance on offer. It will easily climb to speeds that shouldn’t be shared without trying, and still be pulling strong.

But this is no point-and-squirt muscle car. What you become grateful, then, is how planted and resolutely stable it feels; even when surfaces are poor and the ride is set to the almost circuit-tuned Sport Plus mode - which you’ll want because it makes the car tauter, more engaging and more communicative - it doesn’t jump around. Taking it on the same roads on which the XM became a handful was a revelation. The M5 would have smashed the bulky blow-hard.

There’s no doubt that autobahn will be the very best place in which to experience all that this car can express. Yet that something this size and substance can feel so confident on narrow, twisty roads is quite something.

You are still getting your money’s worth from investing in that Active M Differential and it very likely also helps that this is the first M5 with rear-wheel steering, which can deflect the rears by up to 1.5 degrees.

Fans of predecessor M5s will have questions, of course. For one, they will wonder why the development team has taken some of the bark from this bite; the V8 is still able to sound off loudly, with a satisfying snarl at lower revolutions, but it lacks the jagged chatter of the old mill. For another, they’ll also need convincing about why a car that was complex enough in its settings in previous forms is much more so now.

Also, they might lend feed back on the system being set up to tell drivers to take a rest after an hour of brisk driving. A nice idea, but some of the suggested ‘rest stop’ are interesting … in my case, the car determined the three best in my area were two service stations and a Chinese takeaway. Even though the town they were all in had several parks.

Last thing: The paintwork. Frozen Deep Grey adds $7100 to the sticker. It’s an intriguing touch, basically changing hue from deep black-grey to an almost burnished bronze depending on the light. But these frozen finishes can be a bit of a mare; they demand special care (no car wash machines) and because you know just one scratch and it’d be ruined, chances are you’d have to think carefully about wherever you took the car. Better off with a standard hue that could at least be touched up far more easily by a professional.

The price? Well, it’s no small matter, but never has been, and that plus the car’s sheer size is also likely why most of the M fan base prefer the smaller models. Which are also capable of delivering far more performance than you’ll ever know what to do with within the bounds of legality on public roads.

The M5 is a legend. As much as this version may prove controversial amongst loyal fans, there’s nothing to say it’s not wholly worthy of the badge.