Silverstone, Northamptonshire - Having been around since 1963, Porsche's 911 and its derivatives are among the most enduring of classic cars.
And with more than 850 000 having been built over the past five decades, there are plenty of them out there. As with all old cars, they range from pristine to well-used to seriously ratty, while some variants are far more collectable than others - and becoming more so all the time.
Buying one is a real minefield, especially if you're looking for something really special, rather than a neat but not particularly exclusive example to have fun in on weekends. If what you are after is the pleasure of driving a classic Porsche then its mechanical integrity is more important than provenance or originality.
At the other end of the scale, however, you really need to know what to look for if you want to buy a rare or 'celebrity' 911 - one with a history.
In this video filmed at classic Porsche dealer Autofarm, car collector, founder of Evo magazine and Porsche enthusiast Harry Metcalfe - who knows his Targas from his Turbos - puts two seriously collectable air-cooled 911s under the microscope and shows us what to look for, before spending the price of a house on a used car.
ORIGINAL AND UNMOLESTED
The first is a 1972 2.4 S, not a particularly rare or exclusive model, but regarded as one of the best - and most driveable - of the classic 911s.
Metcalfe walks us round the car, looking at the tell-tale signs of originality, explaining what to look for, points out the importance of original paint and where to spot 'hidden' repairs - and how to tell when the car was made by external details that changed from year to year.
This is even more important in South Africa, where an anomaly in the law defines a car's year model as the date it was first registered in South Africa, not the year it was built; with classic cars, these are very unlikely to be the same!
This example is incredibly original and unmolested, given that it's more than 40 years old, elevating it from a driver to a collectable and making it worth around R2.5 million.
The second car is completely different - it's a 1991 964 RS N/GT, one of the first examples off the production line and the very first built to Clubsport specification with factory-fitted roll-cage, racing bucket seats, no carpets and no aircon!
This particular car was presented by Porsche to works endurance racer Ulrich Richter. It's not original; it's recently had an engine rebuild and a glass-out respray in special Porsche blue paint, so Metcalfe shows us how to spot accident damage by checking panel gaps and the lack of factory stickers on the bodyshell, that would confirm its authenticity.
Original or not, because of its exclusivity and its history, the RS is a collector's dream, worth anything up to R5 million.