For the past 40 years, the letter M has signified something special beneath the blue and white BMW badge.

In 1978, the first specific M car, the M1 was unveiled at the Paris motor show . This stunning supercar featured a 204kW 3.5-litre inline six-cylinder engine and spawned its own one-make race series.

Established in 1972 to support BMW’s motorsport activities, the M division initially turned its attention to the iconic E9 3.0-litre CSL ‘Batmobile’ race cars, with huge success in Europe including a class win at LeMans.

And now, with the addition of the M2 , BMW’s M-car range is at its most diverse ever. But, what makes these tri-colour road warriors so special?

The E28 M5 was a high-performance version of BMW’s second-generation 5 Series sedan and featured an updated version of the same 3.5-litre six as found in the M1 – this time with 210kW.

Tuned versions of BMW’s 5 and 6 Series cars followed (E12 M535i, E24 M635 CSi and E28 M535i), but it wasn’t until 1984 that the specific M cars as we know them today started to hit the streets.

The famed E30 M3 even took the 1987 Australian Touring Car championship win.

More road cars meant more race cars, and the success continued.

E82 1M Coupe

E70 X5 M and E71 X6 M

So, now, 44 years on, how does all of that motorsport heritage get distilled into the M cars of today?

The body is the first core change.

All the cars in the current M range are fatter than their ‘ordinary’ equivalents. For example, the M3 is 66mm wider than a standard 3 Series. That’s 3.5cm on each side.

That width means a wider track, front and rear, and of course wider wheels – the rears on the M3 measure 10 inches on each side.

For the most part, aero efficiency and subtlety is placed above any ‘look at me’ rating, as the different front bars and small spoilers are purposeful before they are pretty.

The front of the M4, for instance, helps channel more air to cool the brakes and the twin-turbo six.

And it isn’t just the 317kW motor that is cool under there - there's also mass of carbon fibre bracing and a huge airbox. You don’t get that on a 420i!

In the M2, 3 and 4 you can specify a six-speed manual transmission for no extra cost, but most cars will get the M-tuned dual-clutch transmission and specific transmission lever.

It is not the most user-friendly thing to use around town, but when you are driving at pace, the shifts are fast and brutal.

Using the M-mode settings, you can configure the speed and harshness of the gearbox, suspension, steering and engine performance via the iDrive menu – which can then be called upon using the two shortcut buttons on the steering wheel.

There’s plenty of other M goodies around the cabin, too, but these days you can get much of that as an option on regular models.

The range now spans ten models. The M2 coupe, M3 sedan, M4 coupe and convertible, M5 sedan, M6 coupe, convertible and four-door grand coupe, plus the X5 and X6 M SUVs.

The arrival of the M2 also marks the arrival of the most affordable M car ever.

What will the next 40 years bring?

Probably new additions to the family, and no doubt more motorsport success. But, without question, M will continue to be the most aspirational letter of the alphabet.