Seen together they present a remarkable spectacle of gleaming chrome, polished walnut and wide-eyed headlamps. The cars of the Fredericksen Collection, which went under the hammer of auction house Bonhams last September, represented a remarkable selection of pre-Second World War vehicles. They also achieved a total of DKK162m (£16m), the largest sum ever raised at an auction in Denmark. For car enthusiasts, it was a mouth-watering grouping of classics, but not necessarily one that is unique. 'We see similar collections come on the market every two or three years,' says Jakob Greisen, head of Bonhams' US Motoring Department, who handled the sale. 'What was particularly exciting about this one was that it had been put together with such a clear vision. Henrik Frederiksen has filled every corner of his collecting passion and the cars had also been very well restored.' Among the vehicles that whetted collectors' appetites were a 1914 Mercedes 28/95 Phaeton with a rare wooden body and an unusual 1930 Duesenberg Model J Disappearing Top Roadster. The latter went under the hammer for £1,764,675, making it the most valuable car ever sold at auction in Denmark. Such vehicles are rare survivors from the early era of motoring, explains Greisen: 'Probably around 70-80 per cent of cars in the collectable market were built after 1950. More have survived because more were built, of course, but there's also the fact that people tend to buy what they remember – and there are fewer and fewer who recall what was on the roads before the 1940s.' It is no surprise to learn that the most desirable vehicles have added to their value in recent years. 'If a car has made its mark on time if will always generate interest,' says Greisen. 'People also like brands that are still in business – so 1930s Alfa Romeos or 1920s Bentleys are highly collectible. If a potential buyer in his sixties is looking for a purchase and sees an old Packard or Hispano Suiza, he's probably going to be wondering what it is. With a Bentley, he'll have seen something similar before. The same's true of a Bugatti racer – it's a very recognisable, iconic car – the sort of thing you could show to a random guy in the street and he'd know what it was. 'Another example could be a Dietrich-bodied Packard [from the 1930s] – it's very distinctive and appeals to most collectors, more than something such as a Cadillac Sedan V8 [as favoured by gangster Al Capone] from the same era – which is a big, heavy car for which you might not find a lot of takers.' With that caveat in place, several lesser-known marques performed impressively at last year's Fredericksen sale. Step forward, for example, the 1937 Horch 853 Sport Cabriolet, which went under the hammer for a shade under £330,000. While a well-know brand in the 1930s, Horch's factory was overrun by Soviet troops in 1945 and what was left of its machinery was turned over to making vehicles such as the Trabant – the clunky, fume-shrouded runabout that typified 1970s East Germany. 'Unusual brands such as Horch attract a certain type of buyer,' suggests Greisen. 'A Mercedes of the same era would probably attract a much broader audience. People might well have heard of something such as a Mercedes 540k, but they won't necessarily recognise a Horch.' To highlight the point, he adds that the Danish sale's 1935 Mercedes 500K 'Special Roadster' sold for more than £713,000. While there's an active market for such venerable machines, however, it tends to be something that collectors are not initially drawn towards. Greisen says: 'When they start collecting, the typical person begins with a 1960s sports car, a Porsche 911 or a Jaguar E-Type, for example. After a few years they decide they want to widen their interest and they might well look around for a classic pre-war US car, such as a Mercer Racer – which was capable of doing 80mph back in 1915. Ideally, they want something that stands out in terms of its engineering, its history or simply because it looks good.' The latter factor can include what's underneath the bonnet, he adds. 'People are interested if a car's exciting inside,' he says, 'something such as a 1930s Alfa Romeo is a marvel of engineering – like a Swiss watch.' And, as befits a man who sees plenty of top-notch vintage cars, Geisen has his own favourites. 'I really liked the 1927 Bentley 6½-Litre Bobtail that was part of the Frederiksen auction,' he says (it eventually sold for more than £676,000). 'Two more favourites of mine are the Mercer Raceabout – a sportscar from the 1910s that's very fast and handles extremely well – and the 1931 Alfa 6c 750 – a really nimble car of the era.' And he recommends the challenge involved in driving a car from the pre-war period. 'It's a very different experience. When you buy one the best thing you can do is to keep driving it until you get completely used to what it can and can't do. You have to be a lot more alert than when driving something like a Porsche or a Ferrari from the 1960s or 1970s, which don't differ that much from a modern vehicle, but the reward is that it's a lot more entertaining.' Hopefully, the new owners of Frederiksen's collection will agree. Certainly the man himself hopes his former possessions will continue to bring pleasure for years to come: 'I now have to say goodbye to my wonderful cars,' he says, 'but I couldn't be happier as I know each will bring joy to their new owners.'