Coming off the banking in full flight, straight-eight motor roaring with crazed approval, pushing forward from second to third with all the conviction I can muster, feeling the thrust and seeing that long, silver bonnet sloping away ahead of me, briefly it doesn’t seem real. Nor even close to it. This is not ‘just’ a Mercedes-Benz 300 SLR, but in engineering terms, the ultimate 300 SLR. No journalist has ever been allowed to drive it. Yet here I am: no rules, no chaperon. Just me, Mercedes’ own test track and the SLR, one of the most rare and special cars not only in its unique collection, but the world.

At this title we know the SLR in general and one, chassis 0004/55, in particular. It’s the car in which Stirling Moss and Denis Jenkinson won the 1955 Mille Miglia after which the latter wrote his account, made no copy and dropped it into a postbox in Brescia. So we owe it at least in part to the Italian postal service that probably the greatest single story in the history of motor sport journalism found its way onto the cover of this magazine.

This is not that car. There were 10 SLRs in total, if you include 0009/55 which was never assembled. All survive to this day save 0006/55 which was lost in the Le Mans disaster, though we should remember that chassis 0007/55 and 0008/55 are the unraced Uhlenhaut coupés, which when the latter sold in 2022 fetched £115m, beat the record for the most money ever paid for a car at auction by £75m and made the top 10 of the most expensive items of any kind sold that way. If you’re going to go large, go large.

The car before you is chassis 0010/55. The last SLR. Or, put another way, the first SLR of the 1956 season, for that was its intended purpose. Indeed it was only assembled at the end of 1955 by which time the team had known for months it would not be racing the following year. But even though it never raced, this is a very special SLR indeed.

“The car here is chassis 0010/55. Even though it never raced, this is a very special SLR indeed”

Had the team raced on – and remember the SLR won every round it entered of the 1955 World Sportscar Championship save Le Mans which it was leading by miles when the call came to withdraw – the team would have come to the grid with a car outwardly indistinguishable, but faster by far having been through a dramatic lightweighting programme. The original plan – never realised – was to shed 100kg from a car already weighing in below 900kg, so hardly excessively heavy to begin with.

The modifications made to 0010/55 are too numerous to mention but include an even lighter version of its Elektron magnesium body, the omission of the air brake used at Le Mans and all underbody protection, a lightweight radiator, a smaller alternator, lighter battery, narrower rear brakes, outboard front brakes, the deletion of the second spare wheel carrier, an unpadded seat, smaller alternator and omission of one of its two Bosch horns. All told it brought the car’s dry weight down to 796.5kg, some 62.5kg less than Moss’s Mille Miglia and 83.5kg less than the SLR that won its last race, Moss and Peter Collins teaming up to triumph in the Targa Florio. Assuming a constant power output of 300bhp, that raised its power to weight ratio from 341bhp per tonne to 377bhp, an increase of better than 10%. Had it raced, under the circumstances, and looking at the opposition – primarily a heavier Ferrari and less powerful Maserati – it’s hard indeed to see the ’56 title going anywhere other than straight back to Stuttgart.

How did I find myself in it? I’m still not sure, but I think it started last year when I drove the museum’s 1924 Mercedes (note, not Mercedes-Benz) Targa Florio at the little test track at Brooklands and didn’t make a complete pig’s breakfast of it. I’d had conversations with press officers in both the UK and Germany about the importance of recognising the 70th anniversary of the ’55 win, and also with Marcus Breitschwerdt, head of Mercedes-Benz Heritage whom I’d got to know during his stint as president and CEO of Mercedes-Benz UK. But in the end I just got a call. Could I be in Stuttgart on this particular date. And – do you know? – I thought I probably could.

It’s a Saturday and we have the place to ourselves. This is the famed track with the literally vertically banked corner at one end which we’ll not be going near today. It is punishingly hot but I know the car was designed to cope with the heat of Italy and Sicily so if anything’s going to wilt today, it’s far more likely to be me.

“It’s punishingly hot but I know the car was designed to cope with the heat of Italy and Sicily”

The SLR waits for me, insouciant in the sunshine. As you would expect it is immaculate in its glossy silver clothes. It is an uncommonly beautiful racing car, but I hesitate before applying a superlative, because coming from the same era as the Aston Martin DB3S, long-nose Jaguar D-type, Ferrari 750 Monza and Maserati 300S, how do you choose between them? Certainly there never was an era of more stunning sports racing cars and I just hope that those who saw them in period didn’t take their apparently entirely natural pulchritude for granted. And I’d say I think the SLR is the most purposeful of the lot in its appearance, the most likely to make you leap out of the way like a startled rabbit if you saw one approaching at 175mph on the Mulsanne.

What is remarkable about this occasion is how utterly unremarkable everything around it seems to be. Given what I’m about to do, you might expect endless workshops detailing the history of the car, the intricacies of its mechanical make up, micro-managed instructions on how to drive it, strict limitations on number of laps, revs, how much throttle to use and a small brigade of papers to sign not to mention a lecture on the unique privilege which, for reasons unknown, is about to be visited up on me. But no. None of the above. It’s just me, the SLR, a bloke to show me how it works, and a deserted test track. I’d done more paperwork pulling the ticket out of the machine in the long-term car park earlier this morning.

It’s still intimidating. Not because I wonder whether I’ll be able to handle it, nor even its value, because if you thought too much about that you’d never get behind that wood-rimmed, alloy-spoked wheel. With cars like this, it’s the history or, more specifically, the originality. Because it never raced, it will never have been pulled apart and been fitted with a constant flow of new components. What you see here is what would have been assembled at the end of 1955: a perfect, original SLR, almost every detail there from day one, everything as its makers intended it to be. Bend any of that, and there’s no putting it back.

Its story is brief and simply told. For the first 10 years of its life it appears to have done nothing. Then it was to have been handed over to the Schlumpf Collection in Mulhouse (now the Musée National de l’Automobile) but a last-minute change of heart saw it being substituted for 0005/55 which had competed but not triumphed in the Mille Miglia, Tourist Trophy and Targa Florio. Instead it was confirmed in January 1966 to have been gifted to the Mercedes-Benz museum, that lightweight radiator replaced with a standard item – standard, that is, for a 300 SLR… It travelled to England in July 1967 and was demonstrated at Silverstone over the weekend of the British Grand Prix, driven by none other than Moss and Juan Fangio. Just holding a steering wheel that’s been gripped by those two is quite something, I can tell you. Since then, it’s been looked after by the museum and wheeled out for special occasions, like this year’s 70th anniversary of the Mille Miglia win, where it deputised on the starting ramp in Brescia for the now indefinitely grounded 0004/55, better known as the immortal ‘722’, one of very few cars in the world with claim to being even more valuable than this.

I think you probably know from whence the 300 SLR sprang so I won’t dwell on the back story for long. Besides, its internal ‘W196 S’ codename probably tells you most of what you need to know. Its sister was, of course, the W196 R Formula 1 car. Despite appearances to the contrary and bodywork aside, they really are remarkably similar and their shared parentage is obvious even in the way you have to straddle the transmission tunnel in both single-seat and sports car variants. Their brakes and suspension systems and gearboxes were near identical, leaving the biggest mechanical difference being the cubic capacities of their engines.

“Its sister was the W196 R Formula 1 car. Bodywork aside, they are remarkably similar”

The F1 car, running to a 2.5-litre formula, had a 76mm bore and a 68.8mm stroke to yield a 2497cc swept area, while the SLR was lightly bored and heavily stroked to perfectly square 78x78mm dimensions and a 2982cc capacity. But in most other important regards, the two straight-eight motors were remarkably similar, both being twin overhead camshaft designs with two valves per cylinder with desmodromic actuation and direct fuel injection supplied by Bosch. Both were also installed at a 33 degree cant to the right. The engine in 0010/55 is numbered M/196/68 and has been dyno’d at 294bhp at 7550rpm. You’d think Mercedes would supply a peak permissible rpm figure after which the integrity of the engine could no longer be assured but no; with typical thoroughness it actually provides four. The engine is apparently safe indefinitely at 7000rpm, will tolerate 7400rpm for an entire minute, 7600rpm for just 20 seconds and 7800rpm (if you’re brave enough) for a mere two seconds. For myself, I’ll be steering somewhat clear of even the lowest of these limits.

Access is provided through a small door with a rather complex button you must push down and then pull up to operate. You stand on the seat and lower yourself down onto the seat legs getting further apart as the transmission tunnel broadens ever outwards. The five-speed ZF gearbox is at the back, in unit with the limited slip differential and comes with an insane layout, made all the more wicked for seeming so very, very normal. First, third and fifth are in the forward planes, second and fourth the other side of neutral at the back. Just like any old budget rent-a-car. What could be difficult about that? Only this: second is directly below third, not first, and fourth directly below fifth. Roll that around your brain for a minute. If you’d never driven a normal manual car before, and had developed no muscle memory, it wouldn’t matter at all. But when your every instinct tells you to just pull back from third to get fourth, or come back diagonally across the gate from fifth to select fourth, real trouble awaits. Because in both cases, the gear that’s actually waiting for you is second. The consequences are unimaginable. As if I wasn’t intimidated enough.

Still, look on the bright side: it’s surprisingly spacious in here, more so than most of its rivals, and starting it up is really very straightforward: you flick on the magnetos, thumb a key to turn on the ignition and press a button. There is no cough, no splutter, no churning of the starter motor, but a bang that is loud enough to double your heart rate in a blink. The engine is alive.

“There is no churning of the starter motor, but a bang loud enough to double your heart rate”

It was such a different motor to any other in circulation at the time, with its unfashionable straight-eight configuration, a bottom end cast in two blocks of four, power taken from between the two in pre-war grand prix Alfa fashion and that desmodromic gear that mechanically both opens and then replaces the valves, obviating the need for finicky, unreliable, rev-limiting valve springs. And there’s fuel injection long before any Jaguar, Aston, Maserati or Ferrari sports car got to use it. It had more power than any of them too.

I have no instructions. Just an empty track, a pair of borrowed goggles and my own personal, one of one, lightweight 300 SLR. I select first, pray the clutch is easy, discover it is, and head out.

A few laps to familiarise myself. The track is easy to learn which is something and if you can park the growling, snarling note of the engine in some rarely visited outpost of your brain, you realise the motor is actually quite tractable – I’d stop a long way short of calling it docile – and accelerates strongly from whatever speed you like. The gearchange is superb too, like a sharpened Sabatier through a side of perfectly rare beef. And at this gentle pace, you have time to make sure that lever is never heading where it shouldn’t (though I note Mercedes were sufficiently mindful in period to etch the location of each ratio on top of the alloy ball that tops the lever and sufficiently classy to pick out each in Roman numerals). What will it be like when I’m actually trying? I guess there’s only one way to find out.

At a certain number of revolutions on the Veglia rev-counter – I’m afraid I wasn’t looking, but guess around 4000rpm – the SLR just takes off. Pleasantly engaging performance becomes absolutely ferocious as the straight-eight climbs on the cam and stays there. I’ve been so lucky to drive most of this car’s main rivals – D-type, DB3S and 750 Monza – and don’t remember any of them kicking like this. It’s a real job to stay within my self-imposed 6000rpm rev-limit because the engine clearly just wants to go and go. It’s getting more urgent by the revolution and feels nicely in its stride when I call for the next cog. It feels unbustable too and there are stories of missed shifts and engines surviving visits to five-figure territory, and with that desmodromic gear I’d not be surprised; but I have to remind myself that all the parts flying around inside the straight-eight are well past pensionable age and all engines – even Mercedes-Benz race engines – are only as reliable as their least reliable component.

“That engine, rasping and roaring, not so much encouraging but compelling me to go faster”

I’m still not finding the gears easy. Their selection is fine, but each shift requires two conscious thoughts first, one to reckon which way to move the lever, the other to mentally map out the pattern and confirm your instincts are right. Then it slices deliciously home. Confidence is building, but I’m painfully aware that this is the danger zone. Mastering that gearbox is like learning the Nürburgring: when I was instructing there, it was never the rookies nor the experienced hands who binned it, but those with just a little experience, who think they have learned its way and discover the hard way they have not. That is not going to happen to me today.

But I’m pushing harder in the corners now, feeling the steering come alive with some load in the suspension, feeling the rear squat as I accelerate hard out of each turn. And that engine, rasping and roaring, not so much encouraging but compelling me to go faster. At some unspecified number of revolutions (I was much too busy to look but I’m guessing around 4500) the note hardens as the car is kicked down the track like someone just switched on the afterburners. Just once I go second, third, fourth, fifth, one after the other, hitting my own personal rev limit in each in a crescendo of purest mechanical outpouring, then reverse the process, adding a sharp bark of kicked throttle between each downshift to rev-match the incoming ratio as accurately as I am able. Combined, the sound, the feel and drama are unbelievable.

This could get addictive were it not for the brakes, which are brilliant at instilling the fear of God in me, and not much else. The faster you go the better they are, but if you ever want reminding that despite all other appearances to the contrary, this is still a septuagenarian car you’re driving, that middle pedal will oblige every single time. If it had had discs like those worn by its contemporaries from Jaguar and Aston Martin I wonder whether anyone else would have bothered to turn up.

You’d think I’d never want it to end and with many track tests the moment you head for the pitlane is accompanied by a genuine sense of loss; but not this time. One thing I am quite good at is recognising that moment when I’ve learned all I am going to learn today given the environment I am in; and the moment that thought blossoms in my brain it’s time to head back to base. I’ve not been invited to do this for a laugh and while no one has told me how, nor for how long to drive this car, nor do they need to. In short, the moment I realise I’m driving more for me than for you dear reader, that’s it. Anything else would be an unforgivable indulgence and pose an entirely unjustifiable risk to a car of unfathomable value and unique position not just in Mercedes-Benz’s peerless collection of cars, but the entire history of competition machinery.

And when I’d coasted back to where a small clump of Mercedes men and switched off, my overwhelming emotion was one of relief. The joy came later. And weeks after that extraordinary day, when I look at the pictures and remember what went on, I feel it all over again. The 300 SLR: there was not then, nor has there ever been anything like it, and I am more proud than I can say that just once I was able briefly to make its acquaintance.

Our thanks go to everyone at Mercedes-Benz and Mercedes-Benz Classic who helped make this story possible, and Marcus Breitschwerdt, Frank Scheibner and Sam

Mercedes-benz 300 SLR

Engine 3 litres, straight-eight, naturally aspirated
Chassis Brazed steel tube spaceframe
Power 310bhp
Transmission 5-speed transaxle gearbox
Suspension front Double wishbone, torsion bar springs, telescopic shock absorbers
Suspension rear Single-joint swing axle, longitudinal torsion-bar springs, telescopic shock absorbers
Weight 796.5kg
Max speed 186mph