Image copyright Getty Images Image caption The former law professor has made history by winning the election

With slightly hunched shoulders and an unassuming manner, 59-year-old Tsai Ing-wen doesn't look like a threat to Beijing.

But she has just won Taiwan's presidency and is steely in her belief that Taiwan's future should be determined by its people. This is a direct challenge to China, which still sees the island as a province to be reunified by force if needed.

What Beijing will have to decipher is where exactly Ms Tsai stands on the issue of Taiwan's sovereignty and what her next move will be. She has skilfully avoided clarifying this.

She is not just a mystery to China. Many Taiwanese see her as a quiet enigmatic force, difficult to predict.

She has described herself as someone who likes to walk next to walls to avoid the spotlight and characterised her rapid ascendency in politics as an "accidental life".

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Ms Tsai is Taiwan's first female leader but unlike other Asian women who rose to the top, she didn't come from a political family.

The youngest of 11 children born to the last of her father's four wives, she grew up in a well-to-do family.

Her father ran a successful car repair business and made money investing in land, but insisted she attend public schools to expose her to wider society.

Image copyright Facebook/Tsai Ing-wen Image caption On the campaign trail

She spent the first 30 years of her life deep in academic pursuits: getting a bachelor of law at National Taiwan University, a master's in law at Cornell University in the US and a PhD at the London School of Economics, eventually becoming a law professor.

Her area of expertise and English proficiency meant she was called upon in the 1990s to become a legal consultant for Taiwan's World Trade Organization (WTO) entry negotiations.

So began her entry into public life.

'Mini links' to the mainland

As national security advisor to former President Lee Teng-hui, she helped draft his special state-to-state relations doctrine, in which he defined relations between Beijing and Taipei as that of two countries - a move that angered China.

But under the next president Chen Shui-bian and at one of the worst times for cross-strait relations, Ms Tsai, as head of the Mainland Affairs Council, found a way to work with a hostile China and launched the landmark "Small Mini Links" programme in 2001, which allowed direct ferry transport and trade links between Taiwan's outlying islands and mainland China. She later pushed for the first-ever chartered flights between the two sides.

Image copyright Facebook/Tsai Ing-wen Image caption She helped negotiate Taiwan's entry into the WTO

And in 2003, despite concerns about Taiwan opening up too much too soon to China, Ms Tsai convinced Mr Chen and legislators to revise Taiwan's law governing relations with China, making it legal for Taiwanese businesses to invest in the mainland.

"From her perspective, since this was something people needed and were already doing illegally, she thought the government should develop a law and let people do it legally," said Ho Mei-yueh, a former economics minister who worked closely with Ms Tsai.

Not 'deep-green'

Those who know her say she is practical and flexible with a knack for building consensus.

"She's not someone who will take the initiative to go on stage, but once she sits down at the meeting table, she's the leader, said Mr Ho.

But even those who know her are unclear about her stance on Taiwan's independence.

"She's not anti-China, not deep-green (the colour of the pro-independence DPP), and she's never said she favours Taiwan's independence," said Chang Jing-wen, who has written a book about Ms Tsai's career.

Image copyright Reuters Image caption Ms Tsai is good at building consensus, supporters say

But Ms Tsai makes clear that she holds Taiwan's democracy dear; she agreed to take over the DPP in the throes of crisis in 2008, because she believed that a strong opposition was crucial for democracy.

In a clue to what turned her from a reluctant politician to embracing her destiny, she described in her recently published book how she felt when an elderly restaurant worker donated her entire month's salary of NT$20,000 (US$600) to her campaign: "I will always remember. She said she doesn't ask for anything in return, and only hopes that the DPP will help her protect Taiwan's sovereignty; she wants to keep being a Taiwanese person."

China is paramount

Few expect her to push for independence. Yet, despite intense pressure from China and the establishment KMT party, Ms Tsai has not accepted what Beijing insists is the only basis for future relations - a consensus reached with Taiwan in 1992 that there is only one China, with each side free to interpret what that means. Beijing takes that to mean Taiwan and the mainland are one China.

Yet she has also moved away from her party's and her previous position that no such consensus exists. She will know better than many that China remains paramount: Taiwan badly needs economic agreements from its biggest trade partner, particularly when export markets remain uncertain.

Image copyright Getty Images Image caption Ms Tsai has not said whether she favours Taiwanese independence

Kou Chien-wen, a political science professor at National Chengchi University, speaks of her flexibility: "I don't think she's someone who is strongly ideological. She is very clever."

In a sign of this, when Chinese netizens posted tens of thousands of messages on her Facebook page criticising her during her campaign, Ms Tsai simply posted: "I hope this rare opportunity can help our 'new friends' get a complete view of the democracy, freedom, and diversity of Taiwan. Welcome to the world of Facebook!"

Deep roots

Ironically, Ms Tsai could turn out to be a better partner for Beijing than current President Ma Ying-jeou, who is not trusted by some because his parents came from mainland China and his party is pro-unification. Agreements signed with Ms Tsai will not likely face opposition.

Being a mixture of Taiwan's different ethnic groups, and the descendant of a long-time Taiwanese family, has helped her win the trust of voters. Her father was Hakka, her mother Minnan, and her paternal grandmother was from the Paiwan indigenous tribe.

Image copyright Reuters Image caption She was moved to run for office by a donation from an elderly waiter

But if she is unable to win China's trust, her term could be marked by stalemate, or Beijing could shrink or sever official ties. Tensions could resurface, worrying regional neighbours and affecting ties between Beijing and Washington, which is bound by law to help Taiwan defend itself.

Her book offers a clue to her philosophy. Quoting German sociologist Max Weber, she compared politics to the strong and slow boring of hard boards: "We have to be more patient [and work] steadily, practically, and accurately to achieve the ideal. This is my style."