You won't need me to tell you that there's another BMW M5 just around the corner. It'll have a turbocharged V8 and 600hp. It will have four-wheel drive and an eight-speed automatic gearbox. It'll be as fast as a photon and built like a fallout bunker. But it won't be as good as the E39.
By good, I mean as feelsome or as unprocessed or as affecting. Driven right now, the E39 M5 is every bit the unicorn; perched fortuitously between being neither too old or too new, between being neither too rare or too common and between being an anachronism and a bloody revelation.
Naturally some of it is becoming merely instructive. While it might be 20 years old next year, the E39 is too familiar to be thought compelling or novel inside. By '98, BMW was already high on the bottom line of imperfect plastics, and some of their original softness is turning slowly to tackiness even in this, a mint example.
Ditto the steering - unheralded even in its day for the imprudent use of a recirculating ball rather than the rack and pinion found among other E39s - and rendered nondescript now by the subsequent legion of cleverer hydraulics systems and leaner electronic alternatives.
But that's where the limitations end. The E39 - and the contemporaneous E46, too - constitute one of the few examples of a timeless industrial design to emerge from the disposable, meretricious nineties. The car remains acutely purposeful in the modern sense, without tolerating so much as a single extraneous line.
It yields to excess only where it ought to; in the polished quad exhaust projecting from rear bumper and the satin chrome finish of the still gorgeous 18-inch M Parallel Spoke alloys. There's a unique M-Technic airdam at the front, too - but that's just a reminder of the V8 dug into engine bay like a sapper in a trench.
The 4.9-litre S62 unit is a stroked and bored-out evolution of the 4.4-litre M62 V8 featured in the 540i. But that hardly describes the sonorous, molasses-sweet nature of the engine, which sports an electronically-controlled throttle body for each cylinder and thrums evocatively through the M5's hardpoints.
It outputs 400hp to the rear wheels, but instead of endlessly illuminating the traction control light as the F10 does with interminable regularity, the E39's delivery finds the deck in conducive mood - mostly because its 369lb ft of torque is produced at a distant 3,800rpm rather than troubling the tyres from idle.
Along with the note-perfect soundtrack, it is the palpable lack of turbochargers that nails on the S62's charm. The throttle response alone is worth several minutes of staggered, go-nowhere pedal-pushing. But the V8 behind it is never wound-up or frenetic: the double VANOS valve timing has the power unraveling into the back axle with the granular progressiveness of poured cement. It positively flows - and you sit there, pedal nailed, relishing the heft and gravitas of each passing 1,000rpm with the puckered lips of a man in the middle of an almighty golf swing.
The car orbiting this additive-free masterpiece is similarly organic. The six-speed Getrag gearbox - albeit overlong in the throw - is the ideal foil to the V8, and the sensory pleasure of negotiating with such a mighty engine via a manual transmission and well-oiled clutch pedal can hardly be overstated.
Nevertheless, it is in the chassis that the car's distinctively mechanical appeal bubbles over. Despite having its spring heights reduced over the stock E39 and wearing thicker anti-roll bars and solid balljoints where rubber bushings once sat, the car's lubricated sense of compliance over B road tarmac makes a nonsense of the F10's overwrought adaptive damping.
Granted, its body control is hardly in the same league, but this simply means that you slip over England's terrain at a halfway sane speed rather than blithely barreling across it as you would in its descendent. This distinction, between being immersed in a car's performance and simply letting its monstrous capability wash over you, is at the nucleus of the E39's charisma.
Better still, it comes without the mod con shortcomings that an E30 or E34 might: the (admittedly high-spec) E39 we drove featured remote central locking, heated seats, sat nav, parking sensors, cruise control and - amusingly - a mobile phone connection. Not to mention an ESC system that keeps things civilized in the rain - and at all other times can be completely switched out with a simple solitary button push.
True, BMW's latest heritage car would not come cheap. Its 19k odometer reading is very much the horn on the unicorn's head; a feature that would a middling five-figure sum into an excessively large one. The priciest example among the classifieds has covered 25k - and is up for just shy of £50k.
A more realistic prospect would be something like this wearing still below-average miles and available for Ford Fiesta ST money. But we wouldn't dissuade you from a well-cared for high-miler either, if the VANOS system and timing chains are sound. They currently hover around the £10k mark - a respectably modest price to pay for a thoroughbred, and likely 10 per cent of what a launch edition F90 will cost.
Engine: 4,941cc V8
Transmission: 6-speed manual, rear-wheel drive
Power (hp): 400@7,000rpm
Torque (lb ft): 369@3,800rpm
0-62mph: 4.8 seconds
Top speed: 155mph (limited)
On sale: 1998-2003
Price new: £60,000
Price now: c.£7,500 - £40,000