Lucy Turnbull is facing some tough decisions. Credit:Nic Walker What about not-for-profit interests? Can she continue to chair the Committee for Sydney, a cheer squad for Sydney that actively engages in the planning and policy debate with the state government? Will it lead to perceptions of a conflict, particularly as the Turnbull government says it wants to be more involved in the future of our cities? And how will the Committee for Melbourne feel about Sydney's secret weapon? What of the Grattan Institute, a policy think-tank in Melbourne, on whose board Lucy serves? Or the Packer Foundation, which she joined last year to help manage the Packer family's charitable donations. "I am currently in the process of assessing my role on company boards to ensure there are no conflicts of interest," she says. "We are seeking advice from various sources, and we hope to be in a position to decide in the next fortnight, whether I can keep doing what I am doing," she says.

Mrs Turnbull is a former lord mayor of Sydney. Credit:Nic Walker Among the sources of advice is the Department of Prime Minister and Cabinet as well as lawyers and friends. Clearly giving up Prima Biomedical would be a wrench as Lucy nominates medical and science innovation as one of her passions. But if there is any prospect of government assistance or government grants then that will need to be weighed. "I don't want to do it if there is any perceived conflict of interest," she says. "Some things that I do I really love doing, like chair of the Committee for Sydney and being on the board of the Grattan Institute. They are not for profit positions and roles," she stresses.

We are seeking advice from various sources ... whether I can keep doing what I am doing. Lucy Turnbull "If I have to step down from anything it will be extremely regrettable but it's one of these things that happens. Good governance and transparency and not being in a position of perceived or actual conflict is very important," she says. This is not the first time an Australian leader and his partner have had to deal with this issue. Former prime minister Kevin Rudd's wife, Therese Rein, divested the Australian arm of her business when he became prime minister. The business, which offered employment placements for the disabled was heavily involved with federal government programs. Instead Rein took her business model offshore where then British prime minister Tony Blair had adopted a similar policy of effectively privatising placement services. She recently sold the business for $150 million. The Turnbulls have already had to deal with these sort of issues when Malcolm Turnbull became communications minister. The couple made a decision to sell out of their interests in Web Central following a merger with Melbourne IT.

It's the question most women would like to ask Lucy Turnbull. How do you balance two big careers? "With great difficulty from time to time. You need to have a lot of give and take," she says. This juggling of big ambitions and big careers has been a feature of the Turnbull household for decades. In 1982, between the birth of her first child and her second, Lucy Turnbull decided to do an MBA. "It was probably braver than I thought," she says laughing her trademark belly laugh. "During that time I had to work literally one day of every weekend, and during that time that's when Malcolm was the totally enlightened supportive spouse. He would do an amazing job looking after Alex when I had to do assignments," she says.

Meanwhile Malcolm Turnbull was becoming a successful investment banker. In the 1997, Lucy Turnbull stepped out of the traditional workforce, to write a book Sydney: A Biography of a City, a project that would bring her in touch with then lord mayor of Sydney, Frank Sartor. In 1998 he asked her to run for his Independent Living Sydney party and she became his deputy and later lord mayor, when Sartor resigned to run for state Parliament. But by 2003 Malcolm Turnbull had secured the Liberal preselection for the federal seat of Wentworth. Several senior Labor figures made it clear that they would not countenance her as an independent lord mayor, because of Malcolm's political aspirations. Moves were also afoot to merge City of Sydney with South Sydney Council which was seen as a way of delivering control of the City to Labor.

"They were trying to make it much harder for me, there was no doubt about it. I was not terribly happy about that so I went off and saw Clover [Moore, then independent MP for Sydney] in Macquarie Street. " Lucy Turnbull told her: "The only person who can make a difference here is you. I told her I was very keen to ensure that the Labor Party did not have control of the Town Hall and Macquarie Street." So Lucy and Malcolm swapped roles: she into the business and him into politics But Lucy will not be far from the top job. Asked how much Malcolm seeks her opinion, she replies: "Quite a lot."

"We bounce off each other. We have been married for 35 years. Does he ring me up five times a day to ask me questions, absolutely not. But whenever we are considering major issues or major things, we seek each other's advice and the advice of others as well," she says. There has been much made of whether the Turnbulls will be able to understand what life is really like for most Australians of more modest means. Lucy says they work at keeping in touch. That's why for Malcolm taking public transport whenever he can is really important and a way of keeping in contact with people leading normal everyday lives," he says. "It's also really important the manner in which you engage with people," she says.

"The biggest compliment anyone ever gave me was at the Town hall, when a person who worked there said that I speak to people, whatever their role, in the same voice." As for how the Turnbull's will organise the practicalities of two busy lives, divided between Canberra and Sydney, Lucy snorts with laughter. "That's a very good question. I wish I knew the answer."