John Collison does not seem entirely comfortable with his somewhat impressive claim to fame – he is the world’s youngest self-made billionaire.
Just 27, he otherwise seems a supremely confident business leader and excellent communicator.
But ask him about how wealthy he is, and you sense his awkwardness.
People now ask this a lot and I feel like they always want some really interesting answer – and I have nothing for them, says the Irishman.
People ask ‘how has your life changed?’, and they want me to have taken up some elaborate new hobby, like Faberge egg collecting or yacht racing.
Instead he says he likes going for a run in his spare time, describing it as a very practical, low maintenance hobby.
John is the co-founder of a US-based software business that most people will never have heard of, called Stripe.
He set up and now runs the San Francisco-based company with his older brother Patrick, 29, who is the world’s third youngest self-made billionaire. (Evan Spiegel, 27, the co-founder of social media firm Snapchat, stands between the two brothers as the second-youngest).
Founded in 2011, Stripe is not widely known because it doesn’t sell anything that consumers can buy. Instead its software systems enable companies around the world to accept more easily online payments and to run their websites.
With more than 100,000 global customers, last year it announced a new round of funding that valued the company at $9.2bn (£7bn).
This means that John and Patrick are each worth at least $1.1bn, according to Forbes magazine, which is expert at calculating the wealth of the rich and famous.
Not bad for two brothers who grew up in rural Republic of Ireland, and who both dropped out of university.
Keen computer programmers as teenagers, John and Patrick grew up in a small village in County Tipperary, in the west of the country.
After attending a state secondary school in the city of Limerick, their choice of universities was an indication of their ambition in life.
Not for them a college in Ireland or the UK, they instead both decided to study at top US institutions.
Despite no family connections in the US, Patrick successfully applied to study maths at the prestigious Massachusetts Institute of Technology in Cambridge, near Boston in 2007. Two years later John was accepted nearby, at the equally well respected Harvard University.
John says: It was obviously easier for me because Patrick had already done it, but we’d both developed a bit of wanderlust.
I had considered the UK, but that wasn’t far enough away, it wasn’t wandering enough. And both of us were studious, so going to a top college in the US was always tempting.