The self-confessed Citroen enthusiast - he's never owned anything else - counts the SM as one of the company's most outstanding cars. "It was way ahead of its time," Gladman says. Even today fellow motorists mistake it for a brand new Citroen.
"I've had people come up to me and ask if it's a late model Citroen," he says. "They don't realise it's 40 years old."
Powered by a Maserati V6 engine, the SM was one of the fastest front-wheel drive cars of its day with a top speed of more than 220km/h. It had several pioneering features, a new type of variable assistance power-steering that was ultra-light at low speeds but became more meaty at higher speeds. Like modern-day Citroens, it also had hydro-pneumatic suspension with automatic height adjustment.
The six headlights too had automatic levelling. Apart from the SM, Gladman has a 1985 CX25 and 1998 XM in his Melbourne garage. But the SM is his favourite.
"When I got it 30 years ago it was a bit rough," he says. The right-hand drive conversion was a disaster and the engine was in a bad way.
But Gladman has rectified those problems and his $13,000 purchase is now a sort-after classic. "I don't drive it as much as I should be when I do it feels like a modern car," he says.
"It is a beautiful touring machine." SM prices reflect their rarity as only 12,900 were built between 1970 and 1975. Many sell for more than $40,000 today.
Gladman believes there are only 45 SMs in Australia and very few right-hand drive examples. Contrary to popular belief the SM is not a complicated machine if you know what you are doing.
"Modern cars are far more complicated," Gladman says. "Because the SM is mostly hydraulic with mechanical linkages, it is relatively easy to work on.
"The chassis and gearbox are virtually bulletproof.
"Only the Maserati V6 is a bit complex." The SM was originally unveiled to rave reviews at the 1970 Geneva Motor Show.
Apart from Hollywood stars, French Presidents from Georges Pompidou to Jacques Chirac used two specially modified four-door convertible "presidentielle" models, created by coach builder Henri Chapron.