Just over a month ago, the Singapore Exchange's (SGX) former chief executive Magnus Bocker sounded cheerful in e-mails and was making plans to meet friends in Singapore in October on his return from St Louis in the United States, where he was undergoing medical treatment.

But Mr Bocker, a Swede, did not get to keep those plans. He died of cancer on Wednesday in St Louis, just over a month shy of turning 56.

Those who knew him were shocked to learn of his condition early last year. "What I don't understand is how he could be struck down with such a dreadful disease since he kept fit and he ran the marathon," remisier Alan Goh said.

Mr Bocker had left SGX a few months earlier after 5½ years there to set up boutique investment firm Bilbros Capital Partners.

In 2009, after overseeing the major integration of various Nordic bourses with the US' technologically heavy Nasdaq, he was head-hunted from Wall Street to make big changes at SGX.

Indeed, as the SGX noted in its condolence, Mr Bocker was a "driving force for change". During his tenure, he launched a series of reforms such as scrapping the lunch break to allow for all-day trading - drawing howls of protest from self-employed brokers - and the courting of high-frequency traders to help lift trading liquidity.

He said later that he took such unpopular decisions as "Singapore doesn't have one billion people and as an international centre, it cannot afford to have some of these peculiarities".

His determination in getting the job done was reflected in his decision for him and his family to become permanent residents two years after arriving here. "I cut the lifeline. No house any more in New York and no house in Stockholm."

Mr Richard Teng, former SGX chief regulatory officer and current chief executive of Financial Services Regulatory Authority of Abu Dhabi Global Market, called Mr Bocker "a great friend ... full of life, and a true gentleman".

"As the boss, he was a true visionary, a master tactician and one of the most hard-working CEOs who demanded the best from his team. He drove things from the front, leading the charge to make SGX a world-class exchange and putting Singapore on the world map.

"Magnus personally drove the projects, having conference calls with the bankers in the morning and again in the evening to follow up on the issues and enhancing the pitch for SGX," he said.

Companies attracted to the SGX on his watch included insurance giant Prudential, Hong Kong port operator Hutchison Port Holdings Trust and IHH Healthcare.

Also, unseen by the public were his efforts to build the derivatives side of SGX's business - introducing products such as the China A50 contract which turned SGX into the world's leading futures market for Chinese securities.

He was also key in getting the SGX to promote investor education widely, reckoning that this would enable them to invest their nest- eggs more carefully.

Describing Mr Bocker as a man with a big heart who turned the SGX into the "best-in-class" stock exchange in the region, Securities Investors Association Singapore (Sias) president David Gerald said he was genuinely concerned about small investors. But he wondered if Mr Bocker had perhaps not achieved much of what he had set out to do.

He was referring to an abortive bid early in his tenure to pull off a game-changer by offering A$8.4 billion (then S$11 billion) for the ASX, which runs the Australian stock exchange. But that idea had to be dropped after vehement opposition from the Australian government fuelled by nationalist sentiment.

Mr Bocker said later that the merger would have helped to boost SGX's size considerably. But he was circumspect. "If it doesn't work out, you just have to move on," he said.

The latter part of his watch was marred by the crash of a trio of stocks - Asiasons, Blumont and LionGold - in October 2013, which caused investors to bleed as their market value fell by billions of dollars in a matter of days.

Despite the problems, he was always cheerful and friendly. Perhaps the only time his frustration surfaced was when the bourse was hit by technical glitches, halting trading twice within a month in late 2014 - prompting him to muse if there was some bad luck involved.

Even in the face of illness, he was full of zest for life and continued to be generous with his time in giving advice. He even accepted the post as Sias honorary chairman.

He leaves three adult sons and their mother.