The following year, in partnership with Neville Wran and Nicholas Whitlam, he set up a merchant bank which quickly attracted establishment clients.

His most bruising battle was over John Fairfax following Packer's bid for the publishing empire in 1991. He saved about $450 million worth of American-held Fairfax bonds and earned a fee of $6 million, but fell out with Packer.

In 1994 he helped develop the internet provider Ozemail which he later sold for a big profit.

He went on to become chair and managing director of Goldman Sachs Australia and a partner in the global company - a position that saw him caught up in the collapse of the insurance giant HIH.

Its collapse was largely caused by its buying FAI, which was advised by Turnbull and Goldman Sachs, for an inflated price. The question is whether Turnbull knew FAI was worth much less than was claimed.

A royal commission cleared Turnbull. But the HIH liquidator is suing him and others to try to recover some of the losses. It's a case with potential for embarrassment.

Another bit of quite different unfinished business is the republic.

Turnbull chaired the Australian Republican Movement from 1993 to 2000 and was its high profile public face in the 1999 referendum.

When it failed, he savaged John Howard as "the prime minister who broke this nation's heart".

In 2003, Turnbull, who was the Liberal Party's federal treasurer, ran for preselection against sitting MP Peter King in the seat of Wentworth and, after furious branchstacking on both sides, won.

When he entered federal parliament the next year he was probably, with the exception of Bob Hawke, the best known new MP Australia has had; and, with a fortune estimated around $140 million, the richest.

He soon rose, becoming parliamentary secretary with responsibility for water in 2006 and, in January last year, environment minister.

When Labor returned to power last November and Peter Costello opted for the backbench, Turnbull ran for the leadership against Brendan Nelson and lost by three votes. He became treasury spokesman.

Since then, Nelson has languished in the polls, desperate Liberals have dreamt of Costello changing his mind and Turnbull, after causing his opposite number Wayne Swan some early parliamentary embarrassment, has bided his time.

But few doubted he would try again once he knew Costello was out of the reckoning.

The Liberals have taken a risk in choosing Turnbull.

His energy and capacity are extraordinary. He's done marvellously well, for someone not born into serious money, among some of the toughest players around. He can be charming. It's most unlikely that there are any domestic skeletons.

But he's impatient - he'd hardly been in parliament for five minutes before he was irritating Costello with his own blueprint for tax reform.

He's a bully - fellow republican campaigner Tim Costello recalls: "When you're on the wrong end of Malcolm it's terrifying, the thunder in the face and ... the tongue lashing."

He doesn't suffer fools gladly - and there are always fools in any party room whose sensitivities can't be ignored.

He jumps in without consultation - in the run-up to the leadership contest with Nelson, he said he wanted an apology to the stolen generation without its being discussed by the party. That may have cost him the vote.

Yet the conservative Tony Abbott, from the opposite end of the Liberal's social spectrum, thinks Turnbull is destined for great things, though he can be volcanic. Julie Bishop says he's charismatic. Alexander Downer thinks he's a big talent. A force of nature is a common description.

Whatever he is, Turnbull won't be a safe, cautious leader. He'll go flat out, red in tooth and claw, for what he believes. And lord help anyone who gets in his way.