If you’re going to enjoy life with a new BMW M5, you’re going to have to like buttons: they’re everywhere. Some have strange symbols, others strange acronyms. There’s one for adjusting the dampers, another that scrolls you through five different electronic gearbox settings. A third lets you disable the traction control, a fourth will give you your tyre pressures, while a fifth bypasses all the above to select all your pre-programmed optimum settings.

There are so many buttons — despite the provision of an iDrive controller designed to incorporate all non-essential functions into one control — that you’re at risk of missing the only one that really matters.

It’s not that easy to see, and if you don’t press it you may think this M5 is simply a worthy successor to its much-loved forebear. Its engine still displaces 5 litres and produces 400bhp, but now there are 10 cylinders instead of eight and seven semi-automatic paddle-operated gears instead of six manual ones.

But then you find the sixth button, the one marked “Power”, and suddenly this car’s true agenda becomes clear. Press the button and, thanks to the onboard computer simply changing its settings, what had seemed an entirely adequate 400bhp instantly becomes a certified and certifiable 507bhp. Twenty years ago the first M5 had 286bhp and was the fastest saloon in the world. Now its horsepower bar is 77% higher.

The effect of this is more remarkable even than these bald figures suggest. For while the last M5 had done its best work by 6000rpm, this is where the new M5 starts to get going. The one I drove would hit 8600rpm before demanding another gear, at which point the V10 is howling like some rabid cross between an old Audi quattro rally car and a modern Formula One machine.

BMW says it will hit 62mph in 4.7sec, and all that proves is what a miserably poor measure of performance this is for such a car. Slightly more revealing statistics show it will do 125mph from rest in 15sec and — but for electronic limiting — would top out at 205mph. This from a four-door family car that will cost £61,755 when it goes on sale next May.

Part of me wants to say that this is stupid, that the only reason this car has more than 500bhp is the pathetic need to eclipse the output of its rivals from Audi (RS6: 450bhp) and Mercedes (E55 AMG: 478bhp), but that’s not how it feels. It feels bloody wonderful, and so does most of the rest of the car.

Power for the sake of it is a nonsense, which is why the Mercedes 612bhp CL65 AMG was such a disappointment: it possessed no outstanding dynamic talent save raw, brutal, straight-line speed. The M5 is not like that: its power is just one shot in the cocktail. It’s everything else that makes the whole so captivating.

Most impressive is its handling. The old M5 was nicely balanced, but this is in another league. Grip and composure are in a different class, yet the ride is supple and controlled, not least because BMW cannot equip it with the horrid Bridgestone run-flat tyres that destroy comfort in other Fives. Nor can it be fitted with the annoying and disconcerting BMW active steering system that leaves you never quite knowing how much the wheels will react to any given steering input. For all its buttons and exalted specification, in many ways the M5 is a simple soul at heart, and all the better for it.

Some things aren’t right, however. You don’t get an engine to rev like this without paying the price somewhere, and BMW privately admits it lacks the low-down torque of the old V8. This is less of a problem than the V10’s noise at speed. Despite being geared to reach its top speed in the fifth of its seven gears, you can never quite escape the V10’s voice. It’s fun for a while but a little draining after a few hours.

In addition, the gearbox is not the thing of wonder its seven ratios might suggest. It’s the smoothest yet of BMW’s semi-autos, but compared with the semi-automatic system you can specify on a humble VW Golf it feels a little hesitant.

But none of this can spoil the next true great in the pantheon of sporting BMWs. After the disappointment of the M3 CSL, I had feared BMW was losing its grip on what matters with such cars, but the M5 proves it is back on top of its game. Having been eclipsed by the E55 AMG, the M5 is back where it began 20 years ago, as the greatest sporting saloon on the road.

VITAL STATISTICS

Model: BMW M5
Engine type: V10, 4999cc
Power/Torque: 507bhp @ 7750rpm / 383 lb ft @ 6100rpm
Transmission: Seven-speed SMG semi-automatic
Tyres: 255/40 ZR 19 (f), 285/35 ZR 19 (r)
Fuel/CO2: 19.1mpg (combined) / 357g/km
Acceleration: 0 to 62mph: 4.7sec
Top speed: 155mph (electronically limited)
Price: £61,775
Verdict: The best sports saloon in the world

THE OPPOSITION

Model: Mercedes-Benz E55 AMG, £62,170
For: Explosive performance right around the rev change, stealth styling
Against: No manual option, quality not great for the money

Model: Audi RS6, £59,875
For: Looks great, particularly as an estate, sounds great too
Against: Rather wooden handling, poor ride, based on an old design