It was one of the crucial profitable modifications of profession in enterprise historical past.

In 1964, Fred DeLuca was a 17-year-old medical scholar working in a ironmongery store to assist pay his approach by faculty.

Realising he was not incomes sufficient for his wants, he requested a household buddy, Peter Buck, whether or not he had any shiny money-making concepts.

He later recalled: "Pete said 'Why don't you open a submarine sandwich shop? You sell great sandwiches, and people will come'."

Dr Buck - a nuclear physicist with a PhD - did extra than simply provide recommendation. He gave Mr DeLuca a $1,000 mortgage to open a retailer in Bridgeport, Connecticut.

That was the common-or-garden starting of Subway, now the world's eighth-largest quick meals chain, which this week was purchased by the personal fairness agency Roark Capital for a sum regarded as north of $9.6bn (£7.6bn).

That first store, which opened on 28 August 1964, was known as Pete's Super Submarines and marketed itself with the slogan: "Try one for Pete's sake!"

It obtained off to a flying begin.

Mr DeLuca, a manufacturing unit employee's son, advised the Chicago Tribune in 1985: "On our first day, we ran out of all ingredients and sold 312 sandwiches; foot-long subs with cheese, ham, salami and a variety of vegetables. I'd done a great job of promotion."

Shortly although, the pair realised the positioning of the shop was not ideally suited.

Mr DeLuca recalled: "I picked a horrendous location. The people didn't come back. We'd meet on Monday nights and discuss how we were doing. On one Monday night in February, we met after selling seven sandwiches. That was one sandwich for each employee."

It was at this level the pair took a daring resolution. Rather than shut the shop, they selected to open a second one within the neighbouring city of Fairfield, reasoning that the second would assist promote the existence of the primary.

Brooklyn-born Mr DeLuca, who in his childhood had proven his entrepreneurial aptitude by promoting comedian books to his buddies, went on: "We built the store by supplier credit. I think the suppliers fancied the idea of dealing with a 17-year-old kid. We opened up the new store in May, and both stores started to take off."

A 3rd outlet adopted shortly afterwards - and dealing 50-hour weeks within the shops, Mr DeLuca switched from medical college to the much less time-intensive psychology, wherein he ultimately certified.

After the fourth retailer opened in 1967, the pair shortened the identify of the enterprise - which had already been modified to Pete's Subway - to easily Subway.

The pair then set themselves a goal of reaching 32 shops inside their first decade in enterprise however, eight years in, that they had reached simply 16.

That knowledgeable their subsequent large resolution, which was to start out promoting franchises, emulating the success of McDonald's. They named the franchisor enterprise, in a nod to their backgrounds, Doctor's Associates.

It proved the transfer that paved the best way for the chain's explosive development. Subway opened its one centesimal retailer in 1978 and its 2 hundredth simply three years later in 1981. It now has an estimated 37,000 websites around the globe.

The enterprise catapulted the pair to billionaire standing - however Mr DeLuca died from leukaemia on the age of 67 in 2015. His sister Suzanne Greco, who had been head of operations and analysis and improvement, took over the working of the corporate.

By then, although, Subway was retrenching. Annual gross sales had peaked at $18bn (£14.2bn) in 2012 and went into reverse amid indicators that its home US market had turn into saturated following aggressive growth that drove a few of its opponents to the wall.

Nimbler opponents, similar to Chipotle and Chick-fil-A, took market share from it within the US - and there have been additionally a sequence of ugly disputes with franchisees.

Meanwhile, Jared Fogle, who had fronted its ads for greater than a decade, was jailed in 2016 following a baby pornography scandal.

Ms Greco was unable to stem the decline and was not helped by Dr Buck telling the New York Post in 2017 that, having recognized her since her childhood, he had by no means seen her as Mr DeLuca's "heir apparent".

In 2019, she handed over the reins to John Chidsey, Subway's first chief government from outdoors the 2 households. Mr Chidsey, a former Burger King government, closed unprofitable shops, overhauled the menus, spent extra on promoting and took Subway extra deeply into on-line gross sales, serving to it navigate COVID lockdowns and the following labour shortages - plus meals worth inflation that adopted the worldwide financial system's reopening after the top of the pandemic. In 2022, it returned to gross sales development for the primary time in a decade.

The set off for this week's sale got here in November 2021 when Dr Buck, who famously would eat 5 Subway sandwiches weekly, died on the age of 90 and left his stake within the enterprise to his charitable basis. It nonetheless took till January this 12 months for the corporate to substantiate it was exploring a sale.

The sale proceeds will probably be cut up equally between the Peter and Carmen Lucia Buck Foundation - in addition to Mr DeLuca's widow Elisabeth, who reportedly inherited her late husband's total shareholding.

Roark has loads of expertise of the quick meals and restaurant markets. Companies it has backed personal a lot of different companies within the sector together with Dunkin' Donuts and the Arby's burger chain.

Mr Chidsey advised The Wall Street Journal this week that Subway will probably be run individually from Roark's different restaurant companies.

He advised the paper: "They understand our business. From the family's perspective, it was a compelling offer that I think works for everybody."

Under Roark's possession, Mr Chidsey mentioned, growth can be very a lot again on the agenda for Subway.

It has signed a lot of offers with worldwide franchisees, by which it goals to open about 9,000 eating places, together with 4,000 in China alone in the course of the subsequent twenty years.

He advised the WSJ that Subway may develop to round 60,000 shops worldwide - going into new nations it has not beforehand entered and competing within the broader restaurant trade.

It all feels a great distance from Subway's romantic beginnings.