The scene will be familiar to anyone who has ever been stuck behind a milk lorry, a truck full of sheep and a local bus on a rain swept back road in Wales. And so will that mixed feeling of boredom, discomfort and impatience. The cure, I discovered last week whilst testing the latest crate from Aston Martin, is British Racing Green, Connolly leather and 330 bhp. I was happy at 35 mph, but blissfully euphoric as, to the roar of an eager V8, I swept past the whole convoy on a straight barely 150 yards long. The Aston Martin Virage is the epitome of British sang froid; I want one but I'm not rich enough.

In the seventy-five years since the marque began Astons have never been cheap. It is a traditional company and that is one of the traditions. It is the direct result of another; the very high standard of engineering that is indelibly etched into Aston Martin philosophy. Lionel Martin bought in many component parts, but took them apart, and reassembled them to exacting standards. Those parts that were made in-house were beautifully machined or constructed and the whole car was put together with an emphasis on quality. Aston Martin Lagonda still operate to the same principle, and the quality of the product has in no way diminished over the years.

Those changes that have occurred have been more a result of timely evolution than anything else. However if one made a direct comparison between an early Twenties side-valve and a 1990 Virage, the fact that there has been one fundamental shift of emphasis would become fairly evident. Lionel Martin's vision for his sidevalve cars was that they should perform well by virtue of their light weight and agility, and by having small reliable engines. The Virage is a sporting Grand Tourer with an emphasis on size, grace and power. It is also reliable, but the engine is the best part of 5.5-litres. This change of emphasis has not been sudden by any means. The Virage undoubtedly stands firmly in the traditional line-up of Aston Martins built since the Second World War. And if then one compared the DB1 with the Atom, the C-Type or a late 2-Litre, the line of heritage is easy to trace across that historical barrier.

Although it would be nice to see a small-engined Aston built to the same high standards as the Virage, and therefore more in keeping with pre-war Aston Martin philosophy, the Virage itself is certainly a welcome addition to the marque. Some of the later V8s with their flared wheel arches and skirts were just beginning to verge towards the hairdresser's car look and the Virage certainly recaptures the understated English grace that should be the hallmark of Aston Martin.

Victor Gauntlett gave the green light to the development of the first all-new Aston in two decades back in 1985, but despite the so-called clean drawing board the Aston engineers have clearly been wise enough not to throw out a good thing just for the sake of change. The engine is a result of evolution rather than revolution: the chassis retains the same track and wheelbase as the old V8 and the stylists have taken great care to produce a design that is original and modern, but also traditional, standing very much in line with the car's predecessors. The stylists John Hefferman and Ken Greenley were inspired by the DB4GT, and with good reason since that car's shape is one of the most beautiful of any post-war car designs.

The engine then will be familiar to owners of the old V8, but it has been substantially reworked in the areas of emission and fuel injection. Aston Martin have placed emphasis on the fact that this is the first of their cars to meet worldwide emissions standards. Despite the fitting of a three-way catalytic convertor Aston's engineers, in association with Reeves Callaway of Connecticut, have managed to coax significantly more power out of the unit, and the engine's heads now boast four valves per cylinder. Peak power has increased by some 24 bhp to 330 bhp, and torque has increased by 14% to 365 lb ft at 4000 rpm.

Those who associate Astons with a row of gleaming Weber intake trumpets, and the noise of thirsty carburettors, might be somewhat unenthusiastic about the introduction of fuel injection. They need not be worried, for despite the combined civilising touches of this and a catalytic convertor, the engine retains its slightly untamed feel. The wide bore and the short stroke of this V8 give it a sharp, aggressive growl, rather than the lazy deep bellow of some V8s, and despite the fact that only one turn of the key is sufficient to fire it up, that distinctive noise leaves no room for doubt: you're still in an Aston Martin. Unrefined power still seeps through that poise and glamour.

Not only does the fuel injection relieve you of the old engine's potentially lucky dip starting characteristics, but it gives its reward on the move as well. Pick-up is instantaneous even if you floor the throttle at low revs. Guided by the natural willingness of the engine to gather speed, acceleration is still pretty brisk, but pushing the throttle to the floorboards in second or third gear gives a savage response. There is no lag or coughing hesitation, just instant acceleration.

This responsiveness, coupled with the immense quantities of torque available at low revs, makes the engine particularly rewarding when one is driving hard. Really rapid progress can be made in a state of relative composure; you do not have to wind it up much above 4500 rpm, but there is still a sense of unbridled power, a raw edge that gives the car its character.

The engine will pull to 6300 rpm in top, giving the car a top speed of 155 mph, but it remains in essence a low-down punch per. former. 4500 rpm in top still gives you 120 mph, and I do not feel that it is an engine that encourages being taken to the red line in each gear. It will do it willingly enough, but the rewards are greater if you change earlier and use the unit's innate brute force.

The idiosyncratic ZF manual gearbox only goes to endorse the fact that this is a car whose rewarding performance is found in rhythm and timing rather than in frenetic urgency. I picked the Virage up from the factory in Newport Pagnell, and heading towards Hay-on-Wye it took me every one of the intervening Milton Keynes roundabouts to get a feel for the gearchange. It has that same brutishness as the engine, and is in keeping with the car in the sense that it will never offer full rewards on a brief acquaintance, but even so, I still found it unnecessarily awkward. "What a wimp," I hear you cry, "Aston gearboxes are supposed to be like that." But that isn't necessarily so. Early Aston Martin gearboxes were renowned for how beautifully smooth they were, at least if you got the timing right. Timing does help with the Virage: in fact I found that double de-clutching made downward changes appreciably easier, but the brake travelled a little too far beyond the throttle to make this comfortable when in a hurry. The stiff springing of the lever means that it must be moved positively towards a particular gear, and although the whole thing works better when the car is going fast, changes are certainly better if not rushed.

The Virage's handling perfectly complements the engine's characteristics, in the sense that it is responsive and lively even when well within its limits. There is a broad uncharted territory between feeling close to the limit and actually being there, and this lends the car an enjoyable sense of intrigued You know that the car can be tamed through smooth, composed driving, but you feel like taking it by the scruff of the neck. Will it bite back or will it submit? Each time you take the Virage out you will find out something more about how if behaves. The difference between it and a more ordinary high performance car is the difference between an obvious and memorable tune, and a piece of music that surprises you with a new aspect of its beauty and intricacy each time you hear it.

I tried to do as much as possible of the Journey to Hay-on-Wye on A and B grade roads to get a feel for the car's handling, speed, braking stability etc. We took in wide and fast sweeping A roads, through Banbury, Shipston-on-Stour and Hereford, and twisty one track mountain roads in the Black Mountains near Hay-on-Wye. The Virage was rewarding on all of them, but certainly best suited to the former if only because of the immense weight of the car. It needs fast, essentially predictable, roads where the positioning and braking can be timed accurately and where there is less room for doubt. The car's direction and attitude can be revised and altered whilst cornering at speed, but they cannot be dramatically changed. In fact the responsiveness of the throttle, and the fast, precise steering (just about the best I have ever come across) make the car immense fun in fast corners; it can be kept in check by balancing the two. But on a small country road, arriving in the wrong place at the wrong speed, would be more than simply exciting. An irrelevant point perhaps, because Aston Martin did not mean to build a rally car, but an excellent Grand Tourer, and they have done just that.

The chassis and suspension of the Virage have been evolved from the old V8, although the rear end has been entirely re-engineered with the de Dion rear axle set in a cast alloy frame and located by triangulated link and Watts linkage. The front end is controlled by transverse unequal length wishbones, and an anti-roll bar, and there are co-axial spring shock absorbers all round. The car corners with a natural, very slight understeer, which becomes neutral under power. Other than in very sharp corners one would need to be pushing wildly to get the tail out of shape, although it does feel pleasantly light when balanced on the throttle. Despite their effectiveness I was always conscious that the brakes were hauling up a very large motor car, and was always impressed by the uncomplaining way with which they set about their task. Nevertheless the brakes are yet another aspect of the car that encourage you to drive smoothly and progressively. Demon out-braking manoeuvres are not this machine's cup of tea. Much better to overtake by accelerating blithely past the offending sales rep after the roundabout.

There is probably a medical term for the paranoid condition suffered by motoring journalists who believe they are of abnormal shape after testing too many modern cars. It is nice then to be reassured by the gentlemen at Aston Martin who have built a car of human proportions, and not for long-armed midgets, monkeys or Italians. I drove for two days in the Virage without any aches or strains. The pedals, steering wheel and gearstick are all perfectly positioned. You do not need to crane forward, to crick your legs sideways, or to bash your elbow on the transmission tunnel; merely sit comfortably and the rest will fall easily to hand or foot.

Some other interior details, however, might fall slightly less easily to one's sense of taste, depending of course on who you are. Aston Martin have, perhaps questionably, shied away from the traditional chronograph dials set in a veneer dashboard, and have gone instead for a single unified instrument panel set behind perspex. Although it is well done — the dials are still chronograph, are white on black and are nicely arranged — it nevertheless lacks the romance of previous Aston dashboards.

If this is so, positively Visigoth are the Ford parts bin washer and indicator stalks which should go straight back in the bin, and be replaced by thin chrome bars with moulded bakelite ends. Some of the control switches are also incongruously out of place, as is the cigar lighter, which is really for people who buy used British Leyland Jags and drink port in the afternoon. I still haven't worked out whether this is also true of the on-board computer, which although it is difficult to adjust and read whilst on the move, offers you information which varies from the interesting to the irrelevant. Interesting is the average speed, par for the course are the odometer, trip counter and time of day, redundant are the date and temperature, and utterly irrelevant, given the state of English roadworks, is the estimated time of arrival. In America one can simply divide the distance to be covered by 55. Whether the fuel consumption is interesting or depressing I'm not quite sure, but I certainly turned it off when I wanted to go quickly. Perhaps if you can afford the Virage in the first place you will not be quite so troubled by this minor detail. For the record I averaged 12.5 miles to the gallon over the two days I had the car. This can be whittled away to about 8 or extended to about 20 depending on how much time you spend on full noise.

The rest of the interior is faultless, and pleasingly reminds one of what at least three specialist English car manufacturers can do better than anyone in the world. The roof is lined with green suede, the top of the console to the windscreen is in dark green leather, whilst the seats, doors and rear shelf are upholstered in beige Connolly hide with green piping. There is veneer inlay in the doors and around the instrument panel, the computer and the base of the gearstick. The carpets match the colour of the seats and also have green piping. The boot, which of course has a light, and an impressively complete tool kit, and is sufficient to hold several cases, some golf clubs and a fly-rod, is also lined with beige carpet. If the immensely comfortable seats do not make you feel good, the restrained luxury and tastefulness of the interior will.

Aston Martin have a full order book for the Virage until 1992. If I were paid more it would be even more full. Clearly the Aston Martin recipe works — but why? At £120,000 it is exceptionally expensive. There are machines that will do the same sort of job, at the same sort of speed, and in the same sort of comfort for about a third of the price. And they will probably be less idiosyncratic into the bargain; but therein lies the answer. The Aston Martin Virage is nothing if not individual, and as cars get more and more anonymous, the existence of it and machines like it will become increasingly refreshing. While it can perform its tasks with accomplished efficiency, its true value lies in its class and grace, and that you cannot really quantify in terms of pound notes.