You could always spot them at school. They were the kids set slightly apart in the playground and the classroom, never really fitting in. Rather than run with the pack, kicking a ball around, they were already looking for ways to make money from it.
At our respective schools, we had early-teenage kids who touted rock concert tickets for three times their face value, made and sold their own jewellery, and one chancer who - once he had passed his driving test - would pick up his classmates waiting at the bus-stop in the rain and drive them into the school for the price of their bus fare.
Such pupils were not the most popular children in the class. Neither, with hindsight, were they usually the most memorable. There's something distasteful about youths making a quick buck, showing abnormally early signs of commercial savvy. It reveals an odd sense of priorities, except where they and their families are seriously hard up - which none of the examples we recall was.
So where does this irrepressible enterpreneurial spirit come from? Are people born with it? Is it a response to their parents or upbringing? And, most importantly, can it be acquired? In his 'Smart Luck' feature this month, Andrew Davidson, who has been interviewing Britain's entrepreneurs for more than a decade, considers the common traits he has observed in these individuals. But this a reflective piece rather than a piece of scientific research with incontrovertible results. Neither Andrew nor anyone else with any sense can claim there is a DNA double-helix to be cracked.
Perhaps the impossibility of entrepreneur-gene therapy is just as well. Just think of a nightmare vision where business schools from Birmingham to Bradford produced cloned armies of Bransons and Sugars - clearly beards would be compulsory. No. While we can take some pride in the fact that we are the most entrepreneurial nation in Europe - 5.2% of the adult population engage in entrepreneurial activity compared with 2.2% in France (where they invented the word) - you can't have too many business-builders.
If you look at Coming Up Fast, our monthly section for entrepreneurs, you can see why one of the key traits Davidson identifies is what he calls 'soft resilience'. If CUF consistently shows one thing, it is that things rarely come easy. 'One key to success is failure,' Davidson writes, citing James Dyson as an example. 'Everyone gets knocked back. No-one rises to the top without hindrance.' And, once they've succeeded in creating and building a business, many will sell and go on to the next one. They just cannot help keeping on pushing, whether it be running a paying taxi service to get your mates to school or persuading the nation to rethink the vacuum cleaners and washing machines it wants in its homes.