History of the 7

The first Lotus 7 left the factory on 7th September 1957 and is still in production today as the Caterham 7.

Today, the Caterham Seven is held up as a prime example of the minimalist engineering style of Lotus founder, Colin Chapman.

Colin Chapman

With its steel tube, aluminium clad chassis, it epitomises the philosophy of “less is more”. Over forty years after the original Lotus Seven Mark 1 was launched, it is still the benchmark car for comparison when it comes to evaluating handling, balance, grip, steering and acceleration and all the other attributes of “sporting” cars. Yet, at the time of its launch in 1957, it ranked rather low on the priorities of Chapman. His efforts at the time were concentrated on getting the revolutionary all fibreglass bodied Elite into production and on building successful lightweight racing cars for both sports car racing and Formula 2. Already, the ambition of Formula 1 was close to being achieved.

The Seven was looked on very much as a “bread and butter” project, something to keep the racing department busy in the off season when the demand for customer racing cars dropped. Chapman himself, when asked about the Seven in later years, made the almost disparaging remark that it was the type of design you could “dash off in a weekend”.

In fact, the Seven almost never happened. Lotus’ first “production” car was the Lotus Six. It was a typical. mid 1950’s Clubman Special, steel tubed, aluminium bodied, standard road car components utilised wherever possible and with a variety of engines available depending on the requirements and wealth of the customer. The Six was aimed squarely at the enthusiastic amateur racer, sprinter or hillclimber who drove to each event, competed, and, if the car was still in one piece, drove home again. There were quite a few rivals but, being Chapman designed, the Six became the car to beat in this type of motor sport. It did a lot to establish Lotus’ name as constructors of serious sports cars. Only just over one hundred Sixes were made and production ceased in late 1955. Chapman had no intention of replacing the Six. In fact, the number Seven was reserved for a Formula 2 project which, in the end, was never built.

However, before too long, the clamour for a direct Six successor became too difficult to ignore. By then ,Lotus’ numbering system had advanced up to the model Fifteen. However, it was the streamlined “mini-D Type” Lotus Eleven which was selected as the basis for the new Seven design. Essentially, the Eleven’s attractive wrap-around streamlined aluminium bodywork and outriggers, as designed by Frank Costin, was discarded. This left the tube frame sub-structure which was neatly paneled in giving the basic Seven shape.

However, the first Seven was a bit special. It had a Coventry Climax engine , disc brakes all round and a De-Dion rear suspension. In the hands of Edward Lewis, it dominated hillclimb and sprint events in its first season and, of course, generated much interest from potential customers of a “replica” version. However, when made available to the general public, the Seven emerged as a much lower spec’ car. The Coventry Climax engine was replaced by a humble 40 hp sidevalve Ford 100E, more commonly found in the “upright” Ford Anglia and Prefect small saloon cars. The De Dion rear axle was discarded to be replaced by a solid beam axle from the Nash Metropolitan and drum brakes were fitted on all four wheels.

Despite these mundane underpinnings, the lightweight chassis enabled the car to possess a sprightly performance (by late 50’s standards). John Bolster of Autosport managed a 0 to 60 time of 16.8 seconds! Autocar achieved a 0 to 60 in 16.2 seconds. Maximum speed with a full windscreen was given as 80 mph and 85 mph with aeroscreens.

The Lotus S1 1957-1960

Series 1

The car itself was formally launched at the 1957 Earls Court Motor Show although no actual vehicle was provided for the display stand. The Elite took pride of place, the Seven being displayed only as part of the Lotus brochure; sufficient evidence of Chapman’s priorities if any was needed. However, it was the Seven that kept Lotus going from a cashlow point of view. The Elite was proving a difficult car to “productionise” following the emergence of problems with its all fibreglass construction. As a result, deliveries were delayed. It was the Seven which was keeping Lotus afloat. The basic cost of a Seven was £1,036 fully built and £536 in kit form. Almost inevitably, most were sold as kits, the huge price differential being due to the swingeing Purchase Tax charged on fully built cars. Car components were totally exempt. In fact, the burgeoning kit car industry which emerged in Britain in the 1950’s was very much a product of this tax loophole.

Before long, alternative engines offering more power were made available. The 75 hp 1,100 cc Coventry Climax as already fitted to Lewis’ prototype was one option. In addition, particularly with the American market in mind, the BMC “A” series engine (as fitted to the Austin Healey Sprite - already a good seller in the USA) became another option. Although no more powerful than the Ford 100E, the “A” series possessed more sporty characteristics than the asthmatic Ford and proved a more popular choice. Despite the cash flow being generated by Seven sales, when (eventually) a cost accounting exercise was carried out on Seven production, it was discovered that each car sold was actually losing money for the company. The main problem was the high labour content involved in the manufacture of the all aluminium clad chassis. A radical rethink of the Seven was required.

The Lotus S2 1960-1962

The revised Seven Series 2 emerged in 1960. The main differences compared to the Series 1 were, reduced tubing in the spaceframe, replacement of the aluminium nosecone and wings by fibreglass items, replacement of the Nash Metropolitan rear axle by that from the Standard 10 and locating it by use of a triangulated A frame, shortening of the rear under tray, enlargement of the fuel tank and redesign of the rack and pinion steering allowing the pedal box to be lengthened. All these changes helped reduce the production costs.

Engine options remained much as before although the emergence of the new low-line Ford Anglia with its 105E engine allowed a more modern Ford engine to be offered. The main weakness of the Seven 2 lay with the Standard 10 axle. The unit proved prone to leakage resulting in seized differentials. The problem arose because of the differential housing being prised open under acceleration forces. Most owners were forced to have the axles modified by increasing the strength and number of bolts holding the differential casing together. Despite these shortcomings, the Series 2 sold better than the Series 1.

The car became more known to the public at large, partly because of its appearance in the TV series, “The Prisoner”. However, Lotus as a business was gradually moving away from its roots as a specialist/kit-car manufacturer. By 1966, they had won the Formula One World Championship twice (1963 and 1965), were producing the successful Elan (they never really sorted the Elite) and had moved to a new factory at Hethel in Norfolk. Chapman, who had always “tolerated” the Seven rather than enthusiastically supported it, was now of a mind to discontinue production.

It was at this point that the importance of Caterham Cars and Graham Nearn came to the fore. Almost from the inception of the Seven, Caterham Car Sales had been very involved as dealers of the type. It was Caterham’s undaunted support for the car which prevented its demise in 1966 and, in 1967, they became sole distributors, effectively taking over marketing, promotion and sales from Lotus. However, by 1968, it was seen that the Seven was in need of further updating and plans were afoot to design the Series 3.

The Lotus S3 1968-1970

As often the case with the Seven, availability of components was (and still is, to some extent) the driver behind major redesigns. By 1968, Standard 10 back axles were virtually extinct. A replacement was urgently needed. Also, a new range of Crossflow Ford engines had arrived on the scene. Fitted to the Lotus Cortina GT and later, sporty versions of the new Escort Mk.1, the Crossflow quickly established its credentials. It was the arrival of Formula Ford racing in 1967 which really marked the Crossflow as a desirable engine as it was the standard engine fitted to these racers. The back axle problem was solved by Ford making available to Lotus brand new Escort Mexico units which were ideal, being much stronger than that from the old Standard. The main external difference between the Series 2 and 3 was the widening of the rear wings to accommodate the new, wider axle.

The performance of the Series 3 Sevens was dependent on the engines installed. The 1600cc Crossflow equipped car’s 0 to 60 mph time (in 84 hp single carb’ form) was given as 7.7 seconds. The cream of the bunch however was the Twin Cam Seven SS. Fitted with the 1,588 cc Lotus Twin Cam from the Elan, this Seven pushed out 125 hp and was capable of 0 to 60 in 6.2seconds. It was the most powerful, most expensive (cost was £1,225 - in kit form!) and fastest Seven to date. Only thirteen were officially built and they are recognised today as probably the most desirable of the Lotus built Sevens. By the end of 1969, however, the future of the Seven was again under discussion at Lotus.

Series 4

The Lotus S4 1970-1972

On this occasion, the perceived wisdom at Lotus was that the market for a “Clubman” type road going racer had reduced and what was needed was a more “lifestyle” orientated car. A car more properly aimed at the new “Jet - Set” or “Beautiful People” generation perhaps? Certainly the emergence of “fun” vehicles such as Bond Bugs, Beach Buggies etc in the late 60’s must have influenced the decision making process at Lotus. What emerged was something of a hybrid.

Although designated as the Lotus Seven Series 4, the new car had very little in common with its three predecessors, apart from maybe a continuation of the lightweight and minimal comfort philosophy. In fact, officially the car was given a different Mark number, its correct designation being the Lotus 60. Gone was the steel spaceframe and aluminium body. In its place was a mild steel tubular structure with fabricated stressed steel side panels and front section with an all fibreglass body shell. The bonnet was now hinged rather than lift off and the driver and passenger were more “cosetted” (not a word normally associated with Sevens) Existing Seven fans were somewhat disgruntled by the departure from the original concept but it must be said that most of the magazine reviews of the car were favourable. The motoring hacks looked on the 4 as a distinct improvement and, what’s more, the sales rate actually increased, lending some credence to the basic assumption of the changing customer base. Engine options were retained from the 3. Performance figures showed only slight reduction on the earlier mark, mainly due to the higher basic weight of the car. Yet again, however, problems were emerging for the Seven. Although the sales rate of the Series 4 was higher than for the Series 3, it wasn’t high enough to recoup the development costs which had been greater than anticipated. The curtain was finally coming down on Lotus’ involvement with the Seven.

The Caterham S4 1973-1974

It was now 1971 and Colin Chapman had finally decided that the Seven’s days were definitely numbered. The Series 4 was selling better than its predecessors but the model didn’t really fit into the image of a “supercar” manufacturer. Almost as important, however, was the upcoming introduction of Value Added Tax. VAT was being introduced in April 1973 as part of Britain's entry into the EEC. Unlike Purchase Tax, which it was to replace, VAT did not differentiate between fully assembled cars and cars sold in component form. VAT would apply to both. The last incentive for Lotus retaining a “home assembly” car in their line up was going. However, Chapman did recognise Caterham Cars’ involvement in the Seven. Indeed, the Seven had become that company's main line of business.

In 1971, Chapman offered Graham Nearn first option on taking over production of the Seven when the time was right. That time arrived in June 1973 when the manufacturing rights for the car were formally handed over to Caterham Cars. If the future of the Seven seemed secure, this was not the case as a number of difficulties had still to be overcome. Obviously, the version of the Seven Caterham were committed to produce was the current model i.e. The Series 4. Once the stock of former Lotus components were used, Caterham ran into a problem. The suppliers of the windscreen and hood were unwilling to supply Caterham with the rather small numbers of components required, they were more used to dealing with much bigger orders.

Yet again the Seven looked like it had reached the end of the road. This time, the saving of the car were the original “enthusiast” contingent. Caterham cars had realised that there was a healthy second hand market for the Series 3. It did not take them long to recognise that new production Series 3 cars, provided they were built in the correct numbers, would find a steady market. A quick check with the old suppliers of the various Series 3 components confirmed that all the original tools and jigs were still in existence and that the components could be supplied at economic rates.

The Series 4 became history and, without fanfare, the Series 3 came back into production. These were difficult time for the British economy, the Arab-Israeli war of October 1973 had sent fuel prices spiraling. Luxury and sports car sales suffered as a result. Industry was on three day week causing power cuts, strikes and other inconveniences. However, being small and flexible, Caterham were able to ride the storm and continued to meet the small but steady demand for the car.

The Caterham S3 1974 - onwards

Initially, the Caterham Seven Series 3 was indistinguishable from the Lotus Seven Series 3, save for the badge. Caterham even offered a Lotus Twin Cam version. In line with the previous history of the car, changes were implemented when critical components became unavailable. An examples was the demise of the Mk.1 Escort and the introduction of the Mk.2. This necessitated a change to the latter’s rear axle. Even more drastic was the cessation of the Escort Mk.2 itself and the introduction of the Escort Mk.3. This, being a front wheel driven car, meant that supply of suitable Ford rear axles were destined to dry up soon. The answer came from Leyland whose Morris Marina/Ital rear axle was found to be a suitable replacement. Engine options continued to change.

Although the Ford 1600 Crossflow remained the most popular, when production of the Lotus Twin Cam ceased, an overhead cam development of the of the basic 1600cc Ford block by Vegantune became the “top” Seven. As the 70’s moved into the 80’s other changes came about. In 1982 the “Long Cockpit” was introduced. The interior dimensions of the Seven had been based loosely on Colin Chapman’s 5’ 6’’ frame. By the 1980’s the average male had become taller than his 1950’s counterpart and Caterham reasoned they were losing potential sales to taller customers. The bigger cockpit was achieved by moving the rear bulkhead back by 2 ½ ‘’. Moveable seats were also introduced for the first time. A major engine development in the mid 80’s was the introduction of the Cosworth BDR giving 150 hp in basic form. It was the quickest Seven yet, 0 to 60 being achieved in just over 5 seconds.

Probably the biggest event affecting the Caterham in the 80’s was the relocation of the factory from Caterham town to Dartford in Kent. It was not a moment too soon. Shortly after the move, the old premises was almost completely destroyed by the great hurricane of October 1987. The Classic Development of the car continued. For the first time, computer software was used to evaluate the spaceframe chassis and, as a result, tube dimensions were altered to increase stiffness where required and to save weight. Honeycomb paneling was also introduced.

The De Dion axle made a comeback in the mid 80’s and eventually became the standard specification. The solid rear axle remained a cheaper option and has only very recently come to an end. The supply of Ital axles finally ran out in 2001.Part of the reasoning behind the retention of the solid rear axle was the appearance of a number of rival “Sevenesque” kit-cars which were generally available at cheaper prices than the basic Seven.

The launch of the Classic range of Sevens helped retain a basic model in the line up - as well as pleasing the traditionalists who wanted a car closer to the original Lotus specification. The next major change for the Seven was the introduction of the new technology Rover K series all aluminium block engine. Initially available in 110 hp 1,400cc form, it is now available in both 1,600cc and 1,800cc versions and in various states of tune. When the Cosworth BDR engine ceased production, the choice for its replacement came from Vauxhall. This was the 2,000cc 16 valve twin cam. Even in basic form this engine delivered 165 hp. But it was the top of the range JPE (Jonathan Palmer Evolution) which made the headlines. Pushing out 250hp, the JPE achieved a 0 to 60 mph of 3.46 seconds in 1992. Virtually only one other production car in the world could better that, and that was the £650,000 McLaren F1. Just over 30 JPE’s were made. Most Vauxhall customers opting for the less extreme HPC version, pushing out a “mere” 175 bhp.

When the Vauxhall engine ceased to be available, Caterham produced some highly tuned versions of the Rover K engined cars. In 1,800cc form, the standard “K” delivers 122 bhp. In its most highly tuned version the “K” can produce 230 bhp. This, when coupled with the stripped down Superlight chassis, gives the car a phenomenal performance. Caterham claim a 0 to 60 of 3.4 seconds in their current brochure. In many respects it outshines the JPE, the lower power output being offset by the lighter engine and chassis.

 Cat 21

The Caterham 21

Whilst the story of the Seven appears to be one of the few successes of British motor manufacturing, albeit on a relatively small scale when taking the motor industry as a whole into account, there have been some less than successful projects. The attempts to put a turbocharger into the car in the 80’s proved less than successful, as did experiments with the Ford CVH engine. Probably the biggest disappointment in recent years has been the failure of the enclosed bodied Caterham 21 to find a decent market. As in the case of Lotus and the Series 4, Caterham were trying to broaden the appeal of their products to markets which might not be attracted to a car as basic as a Seven. Unfortunately, the launch of the 21 coincided with Lotus’ launch of their Elise.

Lotus themselves would admit that the Elise was an attempt by them to build a car which echoed the driving attributes of the Seven. Indeed, Sevens were used by Lotus when setting baseline handling characteristics for the Elise. It is indeed ironic that a car inspired by the Lotus/Caterham Seven should essentially torpedo Caterham’s own attempt to widen the Seven’s appeal.

The Caterham SV

However, you can’t keep a good company down and Caterham’s latest attempt to exploit a bigger market has been the introduction of the Seven SVA. Essentially a “bigger” Seven, the look of the original car remains, allied to the retention of the characteristic driving attributes.

Imitation is often stated as being the finest form of flattery. If that is the case, then the number of Caterham Seven look-alikes in existence proves that its basic qualities are something worth imitating. Cars like the Lotus Elise, Mazda MX-5, Rover MGF and Toyota MR-2 show that the traditional two seat sportscar still has a place in the hearts of the car buying public. Caterham Cars helped maintain that level of interest, even when the “big boys” were devoting their efforts to hot hatches and other “sporty” saloons. They were able to reap some of the reward of loyalty to the pure sport scar concept when that market picked up again in the mid 90’s.

No doubt, the Seven will continue to evolve whilst remaining true to Colin Chapman’s original concept of a racing car for the road.


Special thanks to Steve Motts of for allowing us to reproduce this article from his website.

Thanks also to Eric McLoughlin who originally wrote the article.