Christmas road test: Packard-engined Bentley

More powerful than a Bugatti Veyron and the size of a bus, Chris Williams's Packard-engined Bentley can light up the greyest day.

Some 10 minutes after driving Chris Williams's Packard-engined Behemoth my hands were still shaking, my voice was croaking and the cool autumn wind was chilling my sweaty overalls.

My face was cherry red from the infernal heat of the engine and my eyebrows singed from its 24 flaming exhaust stubs. In my entire career I have never driven anything as visceral, as physical or as sheer bloody terrifying as Mavis, the 42-litre Packard-engined Bentley.

This is third outing for Mavis, the tribute to the pre-Second World War aero-engined giants that lapped the Brooklands outer circuit with the bravest of the brave behind their huge, string-bound steering wheels.

Williams built Mavis at weekends and evenings over the last seven years using a Bentley 8-litre chassis, with specially fabricated parts and a V12 Packard engine from an American Second World War motor torpedo boat.

Her debut was at this year's Cholmondely Pageant of Power, where she quickly gained a reputation as a stocking sizzler when flames from her exhaust stubs vapourised man-made under garments as well as welding the trainer laces of those unwise enough to stand too close.

By the time of her second run at Brooklands Museum Wings and Wheels event, she was clearly a lead contender for this year's Christmas road test. With a paddock full of mouth-watering machinery, the crowd voted with their feet and besieged Mavis, Williams and his engineering crew and friend Duncan Round cowering in a far corner.

In fact Mavis was still misbehaving with her huge oil pump filling the cockpit and poor Duncan's trousers, but the sight and sound of this behemoth drew young and old by the score.

Let Williams take up the tale and explain how this extraordinary car came about. "I first saw the engine at Beaulieu," he says. "I think it was Duncan Pitaway who had it and he knew I had the Napier [the Napier Bentley, a fearsome device built in 1968 by David Llewellyn and owned and driven with gusto by Williams since 1999].

"He said 'Hey Williams, don't be a tart, get yourself a proper engine like this'. At that time it had upswept pipes and when he fired it up, this great sheet of flame and snot all went into the air and landed on next-door's white linen table clothes. It made a great noise, got through two gallons in no time and when the hat went round, I thought, 'cooool'.

"But I thought no more about it, it just looked too big. Then, when it came up for sale, I realised it was just down the road and I thought, well you could actually get in something (I think), let's go for it."

"It's a proper 8-litre chassis with new side rails but original fittings and lugs throughout. The engine is a 41.8-litre, V12, with each cylinder at 3.5-litres. It has 'knife and fork' rods, four-pole magneto ignition and a supercharger the side of a dustbin, which runs at 2.4 times the speed of the engine.

The inlet manifold diameter is about six and half inches, that's bigger than my house's septic tank system. It's got three fuel tanks; the main 52-gallon tank and header and scavenge tanks."

Even starting the beast is intimidating. I ask Chris to run through the cockpit drill. It looks like something that should be attacking shipping convoys in the Atlantic approaches.

"The dashboard is primarily aircraft specification," he says. "There's the famous Packard brake-horsepower indicator, which goes up to 2,000bhp. Over here we've got the fuel-tank and fuel-pressure gauges.

"The starting system consists of a trembler coil that gives a whole sheet of sparks into the distributor so something will catch somewhere and that's activated with two buttons on the side of the main binnacle.

"There's the dual magnetos for each bank of cylinders and these switches are their over rides, plus various advance and retards and ignition checking systems. The fire button under the steering wheel is actually a fire button off a Spitfire.

"Here are various temperature gauges for oil and coolant and that bank of fuel switches is for the feed and the return fuel pumps, which drain the scavenge tank into the main tank, or top up the scavenge tank.

"Oh and down here is the 'James Bond' panel, with the boost gauge, which shows the suction as well, plus more oil temperature gauges and the overlocks for the solenoids on the fuel priming system.

"And if you understood the half of that you're a better man than I am…"

Boggling with the responsibility, I gingerly climb into the driver's seat. The Bentley C-type gearbox has a conventional H pattern change with no synchromesh. It's an egregious transmission, tough, reliable and fast when mastered, but not one to suffer fools gladly - get it wrong and you're often best to stop and start again.

Trouble is, the clutch travel is simply massive, so you need to pull yourself up against the steering wheel to get the pedal fully down. On the first run the ratios slot nicely, responding to a little double declutch.

Once you are in top you can leave it there, with over 2000lb ft of torque you can go slow enough in fourth to polish the door knockers of the houses you're passing.

It's a relief to get into top, where Mavis settles into a 70-80mph gait, her bonnet stretching out almost as far as Bruntingthorpe's two-mile runway. It feels like driving a car in Nottingham from somewhere on the Isle of Wight.

The ride is quite comfortable and the body gently floats on its springs while the Packard crackles and pops contentedly and sends small balls of smoke out to each side.

Harry Potter's pyrotechnic wizardry's got nothing on this engine. Look down at the dashboard and you see myriad dials and switches trembling, but nothing seems to be in the red so I give the throttle an exploratory prod.

Wow, Mavis doesn't so much surge forward as leap, the radiator steam changes from a whistle to blast and the engine's note deepens and gains an 'I'm-going-to hurt-you-now' menace.

Yet still the centrifugal supercharger remains dormant, which means the intake air is being inefficiently dragged round the blades. We're barely scratching the surface of what this car can do.

The noise is peculiar, because although it doesn't seem to be a particularly loud, it is all-encompassing cotton wool insulation that sucks the air from around the car making it very difficult to think. It's very easy to bumble along in this growly vacuum without really taking in the fact you are doing well over the national speed limit in a 43-litre, 21-foot 2.7-ton car with a corner in the offing…

Ah yes, the corner. Oh help. I stand on the brakes ("They're a bit poor," says Williams) and Mavis slows imperceptibly. You know something's going on as the front tyres change shape as the weight transfers forward. I turn the wheel.

Nothing doing. I use my shoulders. Nada. I pull back my feet off the pedals, brace my body against the cockpit, rise out of the seat and heave. Slowly the nose starts to turn, but not enough.

I hike out of the cockpit as if Mavis were a racing dinghy and get another few degrees of lock on. By now the weight has transferred to the outside and the I-beam front suspension is pinching its king pins, so the steering (as if such a thing was possible) has got harder.

I fight at the wheel, gleaning another degree or two and finally decide that's probably enough to get us round and get back onto the throttle.

So there I am, in a remarkably peaceful moment, hiked out of the cockpit, hanging on the wheel and contemplating the sheer scale of the accident you could have in this car.

The Packard picks up the pace and brings me back to life by squirting a serpent's tongue of flame, which warps and weaves its way out of the exhaust stub and up towards my face.

Having covered me in oil to make me nice and flammable, Mavis is now trying to set light to me. I had my hair cut the day after the test. "What on earth have you been doing?" asked Max as he surveyed my crispy burnt eyebrows - I didn't dare tell him.

Mavis is a primordial beast, sturm und drang on wheels, but it's also a history lesson, a mechanical panegyric to war-time heroics and those brave exponents of the Brooklands outer circuit such as John Cobb, Sir Malcolm Campbell, Parry Thomas and Count Louis Zborowski. It's beautifully engineered and built, and a credit to Williams and his group of helpers.

Now fully oil-tight, she'll be in action next year and although her calendar is hazy at the moment, we'll let you know where you can see this incredible car. It really is worth the trip.

THE FACTS

Bentley Packard monoposto

Tested: 41.8-litre Packard V12, four-speed Bentley C-type gearbox and a Bentley Speed Six rear axle running in reverse

Price/on sale: Assuming you could track down a Packard engine and an Eight Litre Bentley, in the region of £350,000. It's not for sale

Power/torque: 1,500bhp @ 2,400rpm/ 2,000lb ft @ 2,400rpm

Top speed: 160mph approx

Acceleration: N/A

Fuel economy: 4 gallons per minute at full chat

Verdict: A car for real men. Never mind those cup holders or air conditioning. Who needs seatbelts and airbags? A pair of goggles and gauntlets and a pint glass of pure courage is all a man needs to get to grips with the mighty Mavis. Me? I might be washing my hair on that day if that's OK with you…

Telegraph rating: Five out of five

THE RIVAL

Napier Railton

The only thing that comes close is John Cobb's old 24-litre aero-engined record-breaker, although that seems rather effete compared with the Bentley Packard. Its Napier Lion W12 engine displaces almost half that of the Packard and at a rated output of 530bhp it has almost a third of Mavis's power, but at 5mpg, it delivers the inverse of the Packard's fuel consumption. It was built by acknowledged masters in the field, Thomson and Taylor at Brooklands in 1933 and its aluminium-alloy coachwork was designed by Gurney Nutting. In its pomp, this 16ft 3in, two-ton beast was capable of 168mph and it holds the Brooklands outer circuit lap record in perpetuity.