During the war, the manufacture of sidecars was increased for military use with nearly 10,000 made. Additionally, aircraft and fabrication work had the beneficial side effect of introducing the company to aircraft design and techniques.  Not surprisingly Coventry had been a particular target for bombing raids, and it was necessary to organise rosters of people for what was known as 'fire-watching'.  One such group consisted of Lyons himself, Heynes, Hassan and Claude Baily. Together they made plans for a new engine that would establish the company as a world force.  Early post-war times were difficult for British companies. Amongst other problems were shortages of steel and foreign currency. The Government issued the dictum, 'Export or Die' and steel quotas were closely related to export performance - in other words, no exports, no steel!  Firstly however, it was necessary to resurrect production as soon as possible and the best way to do this was to reintroduce the pre-war range in largely unchanged form. At the same time it was decided to drop the SS name, which had acquired an unfortunate wartime notoriety and simply call the company Jaguar Cars.  Soon after the war the sidecar division was sold and the 11/2, 21/2 and 31/2 litre saloons and dropheads were reintroduced to begin the big export push. The 31/2 litre model proved a little thirsty for the UK market, but was ideal for the USA where the majority were shipped.  The SS 100 model was not produced after the war, but a lone example had been stored, unregistered throughout the war. Known by its subsequent registration, LNW 100, the car was very successful in the Alpine and Tulip Rallies in the hands of Ian Appleyard.

In September 1948 Jaguar announced its first new post-war, stop-gap model. Something more radical was being conceived but various constraints dictated that the Mark V would carry the company's fortunes for a couple of years.  The main innovation was the adoption of independent front suspension, conceived by Heynes.  The exciting new engine was virtually ready for production, but it was considered that the Mark V was a little too conservative to launch it in and so the Saloon and Drophead Mark Vs were offered with the usual 21/2 and 31/2 litre power units.  Lyons had specified that the output from the new engine should be that ultimately achieved with 'Old Number 8', 160 BHP. The designers bravely chose an overhead camshaft layout and after trying several configurations, the final engine was decided upon. It was to be a straight six of 3442 cc and given the name XK.  The achieved output was 160 BHP!  Jaguar now had an excellent new chassis, a tremendously exciting new engine, but no sports car. So the decision was made to produce a small number of sports cars, which would generate publicity and perhaps gain a few competition successes.  The task fell then to William Lyons to design a suitable body in just a couple of months for the 1948  Motor Show. 

The result 'stole the show'. It was known as the XK120 and was destined to become one of the greatest sports cars of all time.  This was no thinly disguised racing machine. It was refined in the usual Jaguar manner, had unrivalled comfort for such a car, and to cap it all, was priced at just £998 (£1,298 with tax).  The name was based on top speed which made it the fastest production car in the world. Indeed at first people were sceptical and refused to believe what was being claimed for the XK120.  To convince the sceptics however, some tangible proof of the claimed prowess was needed. Accordingly Jaguar took over a closed section of dual carriageway at Jabbeke in Belgium where, in front of the assembled press, a standard XK120 proceeded to clock 126 mph. With the windscreen removed 133 mph was achieved and, as if this was not enough, the driver then pottered past the amazed press at a mere 10 mph in top gear.  The orders came flooding in and Jaguar quickly realised that the couple of hundred originally intended could not possibly meet demand. The waiting lists were lengthened still further after the XK's racing debut at Silverstone in a Production Sports Car race. Three cars were loaned by the factory to well known drivers Peter Walker, Leslie Johnson and Prince Bira of Siam. Bira was unlucky enough to have a puncture, but the others finished first and second.

In 1950 it was decided to take three cars to France for the world famous Le Mans 24 hour race, merely to assess their capabilities against international opposition. They were unlucky not to finish in the top three, when the leading example succumbed to clutch trouble after 21 hours. However, valuable lessons had been learnt. 

 
One of six specially prepared XKs had been lent to Tom Wisdom for competition use. He proposed offering the car to a young up-and-coming driver for the famous Dundrod Tourist Trophy race in Ulster.  Jaguar were not too keen as this young man was reputed to be too fast for his own good. Reluctantly they agreed, and in appalling conditions, Stirling Moss left the field behind to take one of the most important wins of his career.  On the rallying front Ian Appleyard had replaced LNW 100 with one of the six special XKs. NUB 120 took Appleyard and Lyons' daughter Pat, to success in the Alpine Rallies of '51 and '52 and the Tulip Rally in '51 and became one of the most successful rally cars of all time.

At the 1950 Motor Show the Mark VII saloon was unveiled and once again Lyons 'stole the show'.  Designed with the US market in mind, it was, by European standards, a very large car. It was certainly a full five-seater but being powered by the now-famous XK engine it was no slow coach.  Americans took to the Mark VII and some $30m worth of orders were taken within months of the car's introduction. Such was the demand that a larger factory was required and the company moved to the present manufacturing plant at Browns Lane, Coventry in 1951/52.  1951 also saw an addition to the XK120 range - The Fixed Head Coupe. As the name implied, the model had a solid roof reminiscent of the one-off SS 100 Coupe prepared for the 1938 Motor Show of pre-war Bugattis.  The long distance capabilities of the Fixed Head Coupe were demonstrably proven when Bill Heynes' own road car was taken to Montlhery Autodrome near Paris. Here Stirling Moss and three others drove the car for seven days and nights at an average speed in excess of 100 mph.

After the three XK120s' exploratory trip to Le Mans in 1950, it was realised that Jaguar had the makings of a successful competition car if weight could be saved and aerodynamics improved. Consequently Lyons was persuaded by Heynes and the Manager of the Service Department, Lofty England, that a car should be produced solely with racing in mind.  Hence was born the XK120C, or as the car is more generally known, the C-type.  To reduce weight, a multi-tubular triangulated frame was chosen and designed by Bob Knight. The body was designed by an aerodynamicist, Malcolm Sayer, who had joined the company from the aircraft industry.  Many components were carried over from the production XKs including, of course, the engine. This, however, was modified with larger exhaust valves, higher lift cams and larger SU carburettors.

Three C-types were finished just in time for Le Mans in 1951. They were to be driven by Stirling Moss (now the team leader) and 'Jolly' Jack Fairman; the Peters, Walker and Whitehead (a couple of gentlemen farmers); and Leslie Johnson with Clemente Biondetti.  The Jaguars were an unknown quantity and the crowd were watching the Ferraris, Talbots and Cunninghams. However, Moss set off at a great rate of knots breaking the lap record and the opposition. An amazing 1,2,3 looked possible until an oil pipe flange broke on Biondetti's car. Then a similar fate befell Moss.  The third car's luck held however and Peter Walker and Peter Whitehead recorded a remarkable victory first time out for the C-types.  Unfortunately the return to France in 1952 did not yield the expected second victory. Concerned about reports of the new Mercedes' straightline speed, Jaguar hastily and unwisely fitted more streamlined bodies but were unable to test them at sustained speeds of 150 mph.  Within hours all three had retired with overheating problems.  Jaguar built a small quantity of 'production' C-types and of the 53 built, including the works cars, a number found their way to the States where they were successfully raced.

In April 1953 a third version of the XK120 joined the Open Two-Seater Super Sports and the Fixed Head Coupe. It was a cross between the two and known as the Drophead Coupe, being a more sophisticated open version.  Meanwhile Jaguar engineers had been working in conjunction with Dunlop on a completely new type of brake that had, as yet, only been used on aircraft.  The new development was the disc brake and was to be Jaguar's secret weapon upon their return to Le Mans in 1953.   The 24 hour race that year was notable for having representatives from most of the leading European motor car manufacturers and most of the top Grand Prix drivers. Rarely, if ever, had the competition been so intense.  With their fade-free brakes the C-types could decelerate at the end of the three and a half mile Mulsanne Straight from speeds of around 150 mph, time after time, with complete confidence and furthermore, they could leave their braking far later than their rivals. The result was a complete walkover, the Jaguars finishing first, second and fourth. 

 
The winning car was driven by a couple who typified the amateur drivers of the era. Major Tony Rolt had won the Military Cross for distinguished war service and Duncan Hamilton was a larger than life character to whom it was very much sport for sport's sake. Moss and Walker finished second after suffering fuel feed trouble early on.  If further proof were needed that Jaguar was now a world force and the XK engine a world beater, then the emphatic triumph of '53 against one of the strongest fields any race had ever seen provided it.