More than three decades later, and to nobody's real surprise within the bank, Flint has been chosen as its chief executive.
Flint says his headmaster introduced him to the CEO of HongKongBank in Indonesia, who advised him to get a degree and join the bank as an "international officer".
"So that's what I did – and I was accepted," he was quoted as saying in an HSBC internal memo following the announcement of his appointment on Thursday.
Armed with a degree in Economics from Portsmouth Polytechnic rather than one of Britain's more high-profile universities, Flint joined HSBC in 1989 and trained in Hong Kong and Calcutta.
The Yorkshire-born executive's approach to business is exemplified by moves like his visit last year to potential customers in Guangzhou and Shenzhen in China at their homes in order to find out about their wealth and banking needs.
"There is no substitute for first-hand, on-the-ground experience if you are curious and want to understand the wider world," Flint was quoted as saying Thursday's memo.
That trait will come in handy for the new chief executive of Europe's biggest bank, as it looks to meet the expectations of regulators, shareholders, and customers, while also growing profits again following a period of restructuring.
The 49-year old, who runs HSBC's retail and wealth management business, it's largest business unit, will take over as CEO in February next year when Stuart Gulliver, 58, retires after seven years in the job.
From bolstering the bank's pivot towards Asia - which is centred around China's Pearl River Delta region - with billions in investments to beefing up digital capabilities and retail banking footprint in key markets, Flint has been central to many of Gulliver's recent strategy decisions.
FOLLOW THE MONEY
Analysts expect little change in the bank's focus, which makes more than half of its profits in Asia, but is facing growing competition from local as well as global peers.
"Flint is very well versed across the bank's many different businesses ...it seems like a very natural, safe appointment," said Benjamin Quinlan, chief executive of Hong Kong-based financial services consultancy Quinlan & Associates.
"The ability to look at HSBC and continue to run it as global universal bank is very important and relative to the background he has, it kind of suggests the fact that they want to continue with their universal banking strategy."
Flint, who is married with two children, has so far maintained a low public profile and spoken little to the media.
Interviews he has given have focused on the future of banking. He told Reuters last year that the industry had fallen behind other sectors when it came to embracing new technology due to the financial crisis.
"We've been a bit distracted. The industry pretty much failed and then we've been in remediation mode and fix mode ever since," he said.
Flint spent the first 14 years of his career with HSBC in Asia, helping to establish and expand the bank's markets business in the region before moving back to London in 2004.
Before becoming the chief executive of retail banking and wealth management in 2013, he worked across different functions that included group treasurer, head of global asset management business and group head of strategy and planning.
Besides Flint, global banking and markets head Samir Assaf, its Europe chief Antonio Simoes and finance director Iain Mackay were among the most often cited contenders for the CEO's role at HSBC in the past year.
Analysts said HSBC's push into Asia, and mainly China, could have influenced the selection of Flint.
"It's been very much about continuity, they have been successful, they continue to be highly profitable as banks go. So why you're going to change something that works?," said Keith Pogson, EY's Asia financial services lead based in Hong Kong.
"Under Stuart (Gulliver), they had a very clear focus on the Pearl River Delta. I would expect under John (Flint) they would continue to take the same course. It's a straight forward message -- follow the money."
(Reporting by Sumeet Chatterjee; editing by Alexander Smith)
By Sumeet Chatterjee