Mel wasn't sure either, though again it rang a bell. And prompted an anecdote of his own that, very neatly, summarises why the 6.9 deserves recognition as more than just an old Merc with a sodding great V8.
Blast from the past
"At the old SMMT Test Day at Silverstone in 1975 or 1976, Mercedes brought a LHD 6.9 with Fangio to drive it," recalls Nichols. "LJKS and I jumped in with him. Leonard sat in the front with Juan Manuel, I was in he back right side and someone else I can't remember in the left rear seat.
"Fangio, driving with one hand, making just tiny movements at the wheel and talking to Leonard all the while, slipped up alongside the Pantera and eased past him. I looked out the side window and grinned at the Pantera driver as we were alongside, just a couple of feet away. I'll never forget the stunned look on his face as he realised he was being overtaken, in the middle of one of racing's most challenging corners, by a Mercedes saloon with four people on board. It was too much for him. He backed off and just trundled around slowly until we did a couple more laps and pulled off the circuit. I wonder if he ever knew it was Fangio behind the 6.9's wheel."
Hints of what made the 6.9 capable of stuff like this can be found lurking in the technical specification, which makes fascinating reading for anyone bothered enough to go beyond that intimidating displacement figure.
That this monster of an engine drove through a three-speed automatic gearbox suggests little more than a crude, four-door muscle car. But the 6.9 is packed with engineering intrigue and eccentricities. Like the fact that the engine was dry-sumped, racer style, both to avoid any unseemly bulges in the S-Class's lines and to stop the 12 litres of oil Mercedes deemed necessary to keep service intervals manageable from slopping about during heavy cornering. This, the complex hydropneumatic self levelling suspension and the limited-slip differential suggested that Mercedes expected owners to do more than simply waft about, the 6.9's popularity among contemporary F1 drivers, most famously James Hunt, suggesting many accepted the challenge.
So how does it measure up today? Thankfully Mercedes communications boss Rob Halloway is as passionate about the brand's older products as he is the new ones. And saw merit in sourcing a 6.9 - this one from Australia - to join the UK fleet to draw a line back to the birth of a spirit that lives on in today's AMGs. Good on you Rob!
When the 450 SEL was brought along to a recent AMG round-up event at Goodwood there wasn't the chance to attempt Fangio-like humiliation of more racy machinery (probably for the best...) on the track. But while the rest of the hacks made a bee-line for anything with a 63 in its name PH had only one car in its sights.
Nearly 40 years on from its debut in 1975 (it should have launched 18 months earlier but that would have been bang in the middle of the oil crisis), the 6.9 has lost none of its ability to surprise those in supposedly faster machinery.
Pottering through a Sussex village at a steady 30, the BMW behind me was probably eyeing the approaching NSL sign and giant, Mercedes shaped rolling roadblock with dismay. I'd barely warmed the car through, was just settling into the springy, velour-trimmed seats and wasn't especially in a rushm but who's to refuse a challenge?
The way the 6.9 gathers speed is most unlike any modern car. But lacks none of the shock and awe it must have had at the time. 286hp doesn't sound so impressive but the 405lb ft of torque is the more important figure here. For all that dominance of the engine there's no sense of drama, no building revs, no V8 burble and no kick in the ribs. Just a slight whirr, a slow, steady movement of the needle on the tiny rev counter and that rather startled BMW suddenly a rapidly diminishing speck in the mirror. Gear changes slur imperceptibly, just a slight twitch in the rev counter announcing that they've even occurred and the big Merc doesn't so much accelerate as build speed. Rapidly.
Corners? Well, warned before departure that this car was yet to have its full mechanical overhaul did cool boots somewhat, huge amounts of play in that gigantic, dimpled steering wheel hardly instilling much confidence, ditto a distinct lack of much levelling going on in that fancy suspension.
Yet on the wide open A-roads around Goodwood discreet yet startling pace was easily maintained with just the tiniest applications of steering and throttle. Two tonnes of 70s Benz moving very quickly indeed remains a suitably incongruous sight but, at its heart, the 6.9 was built for it. As evidenced by the great Leonard Setright in his review in Car. Deciding that more typical use for a 6.9 would involve driving "from some industrialist's reserved park in Ludwigshafen to the Bundesministerium in Bonn for a spot of desk thumping and back in time for Mittagessen" LJK then discussed the thorny issue of fuel consumption with legendary Mercedes engineer Erich Waxenberger, the man often credited with creating the equally awesome 300SEL 6.3.
Fearing the 6.9 would be written off as an "antisocial thirst-raiser" Setright took heart in the fact Waxenberger demonstrated otherwise by recording 11mpg on an Autobahn trip of 124.3 miles in precisely one hour and 10 seconds.
And with blokes like that at the heart of its development how could the 6.9 be anything other than a true hero car?
MERCEDES-BENZ 450SEL 6.9
Engine: 6,834cc V8
Transmission: 3-speed, rear-wheel drive
Power (hp): 286@4,250rpm
Torque (lb ft): 405@3,000rpm
0-62mph: 7.4 sec
Top speed: 140mph
Weight: 1,935kg (DIN)
On sale: 1975-1980
Price new (c. 1977): £21,995
Price now: c. £15-20,000
Track photography by David Shepherd