Now Malcolm, who left school at 16 with just a handful of CSEs, is a qualified psychology counsellor and just a few months away from picking up his OU BSc Hons degree.
But the streetwise former student hasn't given up the day job. As a cabby - at 21, he was once London's youngest - he finds that the fares he picks up every day are a rich source of human material.
The 46-year-old father of two, from Stanmore in North London, says: "I try not to pigeonhole people but once they start talking, my training helps me form opinions. It's fascinating to listen to people and try to get their measure. In fact, it was because I wanted to know what made me tick, on a deeper level, that made me take up the psychology course."
At school, Malcolm became withdrawn and unsociable. "It was mainly because of bullying and anti-Semitism," he says. "As a result, I didn't do well at school, left early and drifted into an incredibly boring job as a civil service clerk.
"My dad was a gambler who lost the family silver, as it were, so I decided I'd go into bookmaking to see things from the other side. That did interest me and I wanted to become a full-time, professional gambler. But I didn't really manage to win much more than my expenses, so was never able to make a decent living at it. After that, I had a brief spell as a menswear salesman and then came the cabbying.
When he was 19, Malcolm began studying The Knowledge, and got a licence as soon as he was legally old enough. He has now been driving a black cab for almost 25 years. It turned out to be a great job for studying. If there were no fares around, he could stick his head in a book, and still does. "My schooldays made me a bit of a loner and the cab is a great place to hide. You don't have to talk to the punters if you don't want to. But when I do, I'm often rewarded with some stimulating conversation."
One of his regular customers is former Chancellor, Norman Lamont. "He's an interesting bloke, but he doesn't know about my interest in psychology. And it wasn't me who took him to that infamous off-licence one Christmas."
In 25 years, Macolm had had all sorts of famous people in the back of his cab. He considers Jackie Onassis to have perhaps been the most interesting. "I thought she was a sad case. At one stage in the journey she even lay on the floor to hide from the paparazzi that were staking out her hotel. I thought she seemed very lonely, but was very, very chatty."
But if his school days made Malcolm insular, his years in the cab and his years of study through the OU have now made him more sociable.
"I'm much more confident now," he says, "and I enjoy chatting to the customers. A few of them know about my background and talk to me about it. I also enjoy chatting to my counselling clients. The OU studies led me to do a course in Rogerian counselling, which I fitted in at weekends and which involved 100 hours of counselling. That's something I would like to take further. Cabbying is a bit of an autopilot job and now I think I'd like to do something more creative - perhaps in finance or sport. They are areas in which I think a psychology background could be put to good use."
Malcolm's enthusiasm for his OU studies also rubbed off on his wife, Sharon, who started her own OU foundation course. Although it didn't last, it gave her a taste for study and she took a teaching qualification, now working as a nursery teacher. She was also very supportive of Malcolm, who spent seven years on his degree, including a year off. "I think any OU student needs family support because of the time invested," Malcolm says. "I know of one chap who spent so much time on his course that his marriage broke up."
At the moment, Malcolm's dreams of getting into the City or sport remain distant. "You can't rush these things," he muses. So next time you raise your hand to an orange light in London, don't give too much away: you might have a psychologist in the front of your cab.