Don’t know about you, but it feels like designers have less of a free reign with concepts than they used to. Modern concepts have to showcase advanced powertrains, lightweight eco credentials and the latest design language.

The concours d’elegance at the Goodwood Festival of Speed features some concepts which are a refreshing change from that. They’re cars from another era, built at a time when all they needed to do was grab some magazine covers.

As a result, they look like something from the Jetsons; you know they’re old, but they still look kind of futuristic.

Vauxhall said some of the design themes developed for the SRV concept of 1970 appeared on the Viva, but I can’t spot them. It was designed by Wayne Cherry as part of the American’s brief to shake up Vauxhall’s design. It featured gullwing doors with hidden door handles, self-levelling suspension and an adjustable aerofoil in the nose. Best of all was that the seats were fixed, but the controls adjust. Over-engineered? You betcha.

Far stranger and less attractive was the Bertone Lancia Sibilo. It was based on a Stratos chassis and dressed in bodywork that resembles a brown wedge of cheese. The glass is painted too, for additional brownness, while the steering wheel has a loudspeaker in the centre.

Peugeot said its 1986 Proxima concept influenced the 405 that was launched a year later. The Proxima’s headlights and grille look familiar, but it’s the button-back seats, sliding glasshouse and vanishing sills that I’m most taken by. That and the 600bhp 2.8-litre mid-mounted V6.

There are few wilder cars than the Silver Fox. Although not concept – it was actually destined to race at Le Mans – it has some of the most outrageous styling features ever applied to a car. You’ll notice the twin-hull design, like a catamaran, with three aero wings in the middle.

Of all the cars here, it’s the Mercedes C111 that was the most engineering-led model. A number of them were used as a testbed for a Merc-developed rotary engine and latterly a diesel unit with which it set a number of speed records. And it is undeniably a pretty car.

As wild as some recent concepts are, will they be shoe-ins for the 2056 Festival of Speed?