(A tantalising but very plausible theory)
When the Isabella was released in June 1954, it was one of the most attractive and modern cars in the world, and also one of the best performers. In 1961 it was still an attractive, highly saleable car, even though its styling was no longer up-to-date – as a comparison with the two newer Borgward Group products, the Lloyd Arabella and the Borgward P100, readily shows. A new model Isabella was due, and it is well known that just such a car was being developed. Just what it would have been like is open to conjecture, but there are some very good indicators that let us piece together a reasonable idea of what it would have been like.
Firstly, a lot of development had been done on the motor. The engineering department had equipped an Isabella with fuel injection, leading to phenomenal performance that far overtaxed even the excellent Isabella suspension. This was one of the main reasons that Borgward developed the Airswing suspension that was used on the big Borgward P100. This air suspension, which was the prototype of what is used on the world’s best cars today, gave remarkable ride and handling. Both air suspension and fuel injection were considered for the Isabella, but it is unlikely that either would have been fitted to it by 1961. More likely is that a new body style with an improved motor would have come first, and then, perhaps five to ten years later, the new engineering developments would have been offered on a top model (similar to BMW’s M-versions) to stimulate sales. 
Similarly, Borgward’s engineers were working on multiple-valve engines, based on the Isabella block, for racing purposes. Had Borgward stayed in production, it is reasonably certain that the Isabella would have been the first production car with a multiple valve engine, and forced the development of this modern technology at least a decade earlier than actually occurred. However, once again, this development would not have been ready for the market by 1961. According to hearsay, racing driver and Borgward owner Stirling Moss, who won the International Formula II Championship with a Borgward-engined Cooper in 1960, kept one of the multi-cylinder, twin-ohc heads under his bed as one of his most prized possessions.
What is known to have been planned for the new Isabella is an overhead camshaft motor. According to all reports, just such a development had been prepared for production in the new Isabella. Adding substance to this report is the fact that a similar motor was used in the BMW 1500 of 1964. BMW succeeded in hiring a large number of Borgward’s engineering staff after Borgward closed, thus regaining its pre-war reputation as the maker one of the world’s best engineered cars. People looking under the bonnet of the new BMW 1500 declared that BMW stood for Borgward macht weiter – Borgward continues on. The engineers had revived the stillborn Borgward engine project. The new BMW engine, known as the M20, remained in production until 1985, and is celebrated as one of the finest engines of its time. Some fifteen years after its introduction, this motor would be upgraded with fuel injection!
What would the new Borgward Isabella have looked like? It is known that a prototype of the new Isabella existed, but after Carl Borgward lost control of his firm, the Experimental Section of the factory was broken into and the new car removed. Its fate is unknown. It was assumed for some years that it had served as the model for the BMW 1500. However, credit for the styling of this car is claimed by Michelotti, who never had a contract with Borgward, and the rather boxy, heavy-looking style of this car is very much out of keeping with the sorts of styles favoured by Carl Borgward.
While most Borgward cars had been styled by Carl Borgward himself, a Lloyd coupe and the prototype new Hansa 1300 (which still exists!) had been styled by the Italian Pietro Frua. Frua had also acted as a consultant in developing the Big Borgward P100 (which was, of course, styled by Borgward). Borgward obviously regarded Frua highly, and if any outside help were sought with styling, then only from Frua. The fact that Carl Borgward, by now 70 years old, was preparing to hand over the running of the firm to his sons Claus and Peter, and his firm’s not having a styling department (other than Carl Borgward himself!) makes it reasonable to expect that Frua would have also received the assignment of styling the new Isabella.
Historian Peter Kurze wrote that Carl Borgward so liked the Hansa prototype, that he wanted an enlarged version of it as the new Isabella. He suggested that the Isabella version would have had more overhang, and this information was quoted in our Australian Borgward book. However, a new book on the life and works of Pietro Frua, written by Detlef Lichtenstein and published by Peter Kurze, brings up a different possibility. Hans Glas, maker of the Goggomobil, recognized that as the micro-car boom came to an end, he would have to move up-market to survive. He turned to none other than Pietro Frua to design a car for him, a car that would fill the gap left by the Borgward Isabella!
Frua came up with a soberly styled, but very well proportioned four-door sedan. From any angle it’s an attractive car, but a family resemblance to the Hansa prototype is obvious. Interestingly, it has a grille very similar to the one proposed for the Hansa 1300! The innovative Hans Glas equipped the car with a very modern motor fitted with a timing belt, a simple but highly efficient design that let him build the motors in his own small factory, and thus set a new direction for modern engine design. The car was first displayed in 1963, and went into production in May 1964. In 1965 a twin-carburetter version called the TS was introduced – clearly a borrowing from Borgward, and doubtless an attempt to win former Isabella buyers.
Glas, when asked if the Glas 1700 were the same car that Frua had designed for Borgward, didn’t deny it, which suggests that it was the same car. However, it must be remembered that Glas could only benefit from any association of his car with the highly regarded Borgward product. Author Detlef Lichtenstein strongly asserts that the Glas 1700 was not based on the Borgward prototype. His only basis for this argument, however, is that the Glas 1700 was very different from the Hansa 1300 prototype! He thus oversees the possibility that Frua could have built two prototypes, one for Goliath-Hansa and one for Borgward. However, this is obviously most likely what happened. 
It is well known that a prototype of the new Isabella existed, and was stolen! The following is quoted (translated) from the book “Kaisen und Borgward” by journalist and author Georg Schmidt, a long-time friend of the Borgward family (Johann Heinrich Döll Verlag, Bremen, 1997). He was interviewing the Borgward family: 
Then there was a pause, until Monica Borgward (Dr. Borgward’s daughter) took up the conversation again. “And then there was the secretive story of the disappearance of the new “Isabella” ....”
Claus Borgward: “Yes, that’s a mystery that hasn’t been solved up to the present day. Here one can see how our father had thought ahead. Or better said, built ahead. Together with his head constructor Heiko Dziggel he had, as was his way of doing things, created a new, improved and even more elegant ‘Isabella’ in his secret chamber. It stood in a locked room, ready to go into series production. Only two people had the key to the room, my father and Director Wilhelm Gieschen – so that no disaster with a too-early publication could occur – people from he press are like wild animals when they sense that there’s something new coming! And the new Isabella would have been a sensation! Yes, and one day the lock was broken open and the ‘Isabella’ had disappeared. It was intended to be a huge commercial success if it sold, and it would have done that, if only..... Today that’s all gone and finished. Snow from last winter....”
This writer’s theory (and it is only a theory!) is that Frua, with the permission and cooperation of the new management that had assumed control of the Borgward works, retrieved the Isabella prototype, made a few changes and presented it as the new Glas! Lichtenstein says that Frua had prepared the new Glas prototype in ‘Windeseile’ – at the speed of the wind! Not hard to do, if the car already existed. It is likely that the original Borgward prototype had had a rhombus in the grille, to preserve the strong model identity that Borgward had had since before the War. 
Frua also designed a stylish coupe for Glas. Could this have been considered as the replacement for the legendary Isabella Coupé? Here we’re really getting into the field of wild conjecture, but it’s an interesting possibility.
Unfortunately, the small firm of Glas was overextended by the development of the new model, and got into financial difficulties. The firm was swallowed up by BMW, which rebuilt the Glas factory at Dingolfing, and still uses it today. The Glas range was re-badged as BMWs, but the Glas engines were replaced with BMW units. If my conjecture about the origins of the Glas is correct, this gives us one of the most amazing pieces of happenchance of automotive history. The car that should have been the new Isabella was finally united with the motor that should have gone into the new Isabella! Faithful Borgward enthusiasts had a chance to buy a new Isabella, and didn’t even realize it. The surrogate Isabella was obviously competing with BMW’s own “Neue Klasse” 1500 to 2000 models, so the tooling was soon shipped to BMW’s factory in South Africa and built there under the name of BMW Cheetah from 1968 until 1973. South Africa had been one of Borgward’s strongest and most loyal export markets, so if the new car had had the Borgward grille and name, it might have sold even better. Whether sold as a Glas or a BMW, it was still a superb car, thoroughly in keeping with the tastes of its time. It would have ensured strong growth of Borgward’s sales, if that company had not been deliberately destroyed by malicious interference.
Today, Glas 1700s are prized collectors’ items, but maybe the BMW 1700 is more interesting for us Borgward enthusiasts. Question: if somebody fitted a BMW 1700 with a Borward P100 grille, would we be justified in accepting it as a 1970 Borgward Isabella?   Tantalising thought!
Written by Marius Venz; Copyright © 2010 Borgward Car Club of Australia Inc. The use of this article by other not-for profit car clubs is permitted provided full credit is given.