It’s clearly an E46 CSL, and they did that one. Built 1,383 of them in fact. It was the first M3 to have a carbon roof, accompanying the famous carbon airbox.

The greatest M car there’s ever been, some say, certainly the one that epitomises M’s brand values most faithfully. The most accurate expression of Coupe Sport Lightweight, too.

Its beating heart was the famous S54 3.2-litre straight six, producing 360bhp (the extra 17bhp thanks to its freer breathing).BMW E46

But not this one. This one is pure skunkworks. M never had any intention of presenting it to the board.BMW E46

Because it has a V8 in it. Lord alone knows why, but somehow they’ve crammed the E39 M5's S62 400bhp 5.0-litre in here.

The packaging is just ridiculous, the clearances measured in millimetres. Maybe it started as a ‘bet you can’t fit that in there’ joke and someone ran with it.BMW E46

I started it up and drove it around – it’s angrier than in the E39, revs and responds faster. Remember they did an M3 GTR homologation with a V8, 10 cars built for the US market

An entirely separate project apparently, as that used a race-tuned 460bhp 4.0-litre motor. This, you get the sense, was for internal enjoym… er,  use, only.

You expect this Frankenstein to be crudely finished, but of course it’s not, so I expect the suspension was altered to rebalance the dynamics.

It's subtle work, the only outward sign an extra hole on the right hand side of the bumper, the standard CSL famously having just one.BMW E46

But here’s the bit I like best: it’s covered 30,000km. Someone was clearly having fun with it.But here’s the bit I like best: it’s covered 30,000km. Someone was clearly having fun with it.

The first M3 (E30 generation) was introduced in 1986, followed by the second (E36), which was presented in 1992. BMW E46

The E30 was a racing car in disguise, a homologation special built by BMW so its M Performance division could race.BMW E46

So, BMW made M3 into a much more mature, faster, and comfortable model when the second generation arrived.BMW E46

For the successor, the E46 M3, the company decided to go all out and create it almost from scratch with a host of individual parts and components.