The 44-year-old O'Sullivan, or 'Pos', as he likes to be called, is not married but holds dual Irish and Australian citizenship.

He was born in Dublin, where his father was a senior public servant who had his children take up odd jobs to supplement their household income.

"I've sold everything from newspapers to French wine and Irish peat fuel, " he says.

O'Sullivan was awarded a first-class honours degree in Economics at Dublin's Trinity College and is a graduate of the worldrenowned Harvard Business School's Advanced Management Program.

Unlike chief executives from Optus' rivals, O'Sullivan has not worked in the telecommunications industry his whole career.

He joined Optus in 1994 to set up the Optus World retail chain, but left the following year after being restructured out of the company. In 1996, he joined a project team at Colonial Group in New South Wales.

Before that, he held various international management roles with the Royal Dutch Shell Group in Canada, the Middle East, Australia and the United Kingdom.

In 1998, he returned to Optus, Australia's second biggest telecommunications company and moved to Sydney. O'Sullivan says he liked Australia, liked the telecommunications industry and liked Optus, so he stayed. "I love to win and rarely ever contemplate losing, " he says.

"I believe in doing what it takes to get results . . . and I frankly believe this is possible without working absurd hours. I also lead a busy life outside work; my way of unwinding is to swim at least six kilometres a week. Despite my advancing middle age, I even manage an occasional game of water polo."

O'Sullivan was appointed to the role of chief executive in September 2004, for a company with 9,000 employees and a turnover exceeding 3.5bn (Aus$6.4bn). If Optus is to stay relevant, he will have to show strategic direction, strong leadership in cost-cutting and new ways to build revenue. This will be his biggest career challenge, given that Optus is a wholly-owned subsidiary of Singapore Telecommunications.

"I spent most of my professional life, including my time in Ireland, wanting to work with businesses that make a difference, " he says. "Not only is it an interesting product, it changes the way people live and think."

As chief executive, O'Sullivan has kept a low profile. He describes his management style as that of a coach but not a leader.

"I see myself as being the 'head coach' of Optus, " O'Sullivan says. "A head coach has the right game plan, the right players available, gets people fit, is responsible for executing the game plan, and anticipating how the other teams and opponents are changing the game.

"Optus is all about innovations, and my management style is demanding but fair. It's all about the team and Optus is one of Australia's leading companies, with a great depth of talent. People outside the organisation think I am extremely hands-on."

O'Sullivan's talent has not gone unnoticed in Australia and overseas, where speculation persists linking him with a move to Singapore's national telco SingTel. It has made no secret of its ambition to secure O'Sullivan's services on a long-term contract, which has fuelled the current speculation in both countries.

Singapore media has reported that O'Sullivan was one of several candidates to take the top job after SingTel chief executive Lee Hsien Yang announced his intention to step down last Friday. The Australian business plays an important part in SingTel's bottom line, accounting for about a third of the group's earnings.

Optus refused to disclose the terms of O'Sullivan's contract, but in Australia, the average chief executive salary is at least 2m per annum, and O'Sullivan is thought to be earning well over that figure.

SingTel purchased Optus for Aus$16bn (around 9bn) in 2001.

O'Sullivan refused to be drawn on the rumours suggesting that he could jump ship to join SingTel, but it is known that he is a member of the company's Group Management Committee.

"My future career ambition is to be a part of the team that will drive the outcome to present Optus back to the market in a few years time as a company with a much more broadly based earning stream, " he says.

"I don't want to comment on speculation."

O'Sullivan first came to prominence in his previous role with Optus as the company's chief operating officer.

During his tenure, he reversed the company's previous losses with a Aus$400m ( 2.34m) turnaround, and delivered its first-ever positive cash flow. The turnaround was achieved while continuing to grow revenues at three times the Australian Telecommunications industry average.

"We are moving to a world in which every home, business, school and hospital will be able to receive massive . . . and growing . . . amounts of data, " he says.

"This technology will change the way we live and the way we do business. My goal is to enjoy the challenge and fulfilment of persuading consumers to adapt to a superior value proposition, and I enjoy being part of a highly motivated team. As long as those conditions are met, I'll happily work anywhere."

Optus's biggest income earner, mobile phones, is reaching saturation and will become more competitive in the next few years.

The next big thing is broadband, and O'Sullivan has taken the risky stance of refusing the commit Optus to building its own broadband network. He is confident that Australia will have three broadband internet operators by 2008 . . . none with more than 50% of the market . . . and national broadband networks extending to more than 500 exchanges.

O'Sullivan has been pivotal in making Optus profitable. Now he has to figure out how to preserve the company's status as the number-two carrier in Australia and maintain its status as a challenger. He will need to do some fast work in the next 12 months, but, if history is anything to go by, he will do well.