Even Lau seems surprised by her rapid rise. 'Ten years after I qualified as an accountant I became a CFO which is unreal. It usually takes longer than that - so I was lucky to have been offered the opportunity.'

But it was clearly more than luck that got her that job.

Lau grew up in her family's home in Ho Man Tin. Her father inherited his father's business importing frozen food from around the world and selling it to wholesalers and retail customers.

Lau went to the best girl's school in Hong Kong - the Diocesan Girls' School - and then on to James Allen's Girls' School in Dulwich, London, before studying mathematics and theoretical computing at Oxford. She loved mathematics and her course at Oxford, she says, remains the biggest intellectual challenge she has faced.

She joined what is now called PricewaterhouseCoopers (PWC) preparing tax returns for England's rich. But after qualifying as an auditor she contemplated moving on. 'I am not a person that enjoys repetition. I need something new every so often, that takes me to a new level of learning. That gets me excited,' she said.

Her bosses at PWC wanted her to stay with the company and offered her a new challenge in the mergers and acquisitions department.

She worked 18 hours a day on deals. 'I got a buzz out of it - it was so adrenalin-driven. There'd be a big celebration after each transaction - then you'd see your work reported in the Financial Times the next day. In my 20s that was really exciting.'

Her job was to structure the deals in the most tax-efficient way. It made M&A exciting and less repetitive than auditing as every deal was different.

But after 2 1/2 years she was again contemplating moving on.

PWC was preparing a partnership programme for her which would have meant being a partner before she was 30, which would have been unusual. 'I was very appreciative of it but didn't feel I was ready for it - I didn't see myself leading the firm yet - which I would expect a partner to do.'

But what had begun to intrigue Lau during the numerous M&A deals she did was why companies were doing the deal in the first place rather than some other deal, and she realised that what really interested her was strategy.

So she decided to go and learn about strategy and joined McKinsey & Co, one of the world's top strategy houses. She spent the next three years working in the luxury retail and heavy industry sectors, first in London and then in Asia, where she developed strategies for mainly multinational clients looking to expand in Asia.

While working on a project for Alcoa the company was so impressed with her work that she was invited to apply for the position of chief financial officer for Alcoa's rolled products division.

'I didn't have the 20-year finance track record to even warrant going for an interview like this. But if they were bold enough to offer me a chance, why would I refuse?' says Lau.

She took the job knowing that she would have to prove herself in the eyes of her mainly white male colleagues. Lau says there was some scepticism at first.

'[And] rightly so - though it didn't feel very good at the time,' she says. But the top management team have been very supportive and Alcoa values having a diverse management team.

'If you believe the statistics, which I do, they show that big companies which are diverse in terms of the gender and ethnicity of their management teams do much better in terms of bottom line results than those which are completely white and male. If that's not a convincing argument then I don't know what is.'

Alcoa has an international senior management team. The previous chairman was Brazilian, the current chairman and chief executive Klaus Kleinfeld is German and the rolled products president, Helmut Wieser, is Austrian.

Three months into her Alcoa job Lau faced a severe challenge with the onset of the global financial crisis. She was still trying to establish herself within the company but swift and decisive action was required.

'We had to take out a lot of costs; headcount - nearly 5,000 employees - because the only way to keep our business efficient was to take out the cost. It was the same for a lot of other companies,' she says somewhat dispassionately.

Lau says a big difference between working for McKinsey and Alcoa is, 'In Alcoa you feel the joy and the pain.'

She no longer has the frustration of working on strategy only for the company not to go ahead with the project. But if Alcoa decides to pursue a particular strategy she has to live out the consequences.

'If it's wrong - whoops. If it hits us on the bottom line we have to explain ourselves to the board.'

In a company of Alcoa's size she has to interact with many different levels of management all at the same time. Below her there are numerous teams which report to her. To get things done Lau had to learn to take more risk and to trust in her teams.

'At McKinsey I could run teams but at Alcoa I have teams in every time zone, so you need to learn to leverage a much bigger organisation. There are 15,000 employees in my group,' she says.

Although her title is CFO she spends a lot of her time on business strategy.

'CFOs these days can't just be boxed-in looking at numbers. They need to be international in their outlook, broad in their thinking and need to drive innovation.'

Her job requires frequent travelling to visit the company's facilities. 'You can't strategise on paper and just imagine what it's like on the shop floor.'

It is important, she says, to listen to the people and to find out what it is that drives product quality and why something is doing well or why there are bottlenecks.

'I can sit at my desk and look at numbers and wish they were better. But how to make them so? It is not just a question of cutting costs. You have to go there and see for yourself. Maybe you shouldn't be cutting costs but spending more to upgrade facilities.'

On her site visits she challenges her management teams to do better, to innovate and 'tell me why it is not possible for us to improve'.

Good managers, she says, have to be well rounded. 'You don't need to be the smartest. You just need to surround yourself with really smart people who share the same vision as you and who are willing to work with you along the same path.'

One country in which Lau is closely involved with the strategy is China.

China as a market has enormous potential but it's a market that 'learns frighteningly fast,' she says.

So it is pointless going for low-margin products. Alcoa has a lot of in-house expertise and a lot of proprietary ways of doing things. 'We have to go for high value products that are hard for anyone to copy.'

But even then she says the market is so dynamic that Alcoa is not going to win with the same product for 10-15 years. 'You have to innovate continuously.'

That's why Alcoa has re-thought the aluminium beverage can and is now producing aluminium bottles that have been taken up by Heineken and Coca-Cola.

In terms of packaging - mainly comprising drinks' cans - the US consumes 5kg of aluminium per capita, Russia just 1kg, and China 0.2kg. So if China begins to consume more aluminium per capita Lau says there is significant upside for Alcoa.

Alcoa produces sheet for cans and commercial transportation. In addition two products that she says gives Alcoa an edge are aluminium brazing sheets which are used in motor vehicle cooling systems; and digital lithographic sheets, which are used to make plates for high-quality magazine printing.

'We are the only company making this product. It has enormous potential,' she says.

Another area she thinks that has potential is consumer electronics. 'Aluminium looks cool, dissipates heat, and can be coloured. And just look at the number of times young people in Asia change their phones - almost every six months.' She sees potential for laptops, the backs of flat panel televisions and mobile phones.

Lau notes that in China's current five-year plan there is considerable detail on sustainability, cutting emissions, clean and green and so on.

'I get excited because aluminium is a material that will help achieve these aims.'

When she's not flying round the world visiting her company's operations she occupies her spare time reading and going to concerts and musicals in New York.

'I feel I need to take more responsibility for my continuous training or I'll fall behind.' So she reads business magazines and books that her colleagues recommend. She also reads novels, swims, plays table tennis, and jogs occasionally - though laments the lack of time for more sport.

Her passion for music has drawn her into assisting arts groups with the business side of their operations, helping them on a voluntary basis to prepare business plans.

This month Lau will have been in her job for three years, the time she normally starts casting around for her next challenge.

'At the moment I feel professionally very fulfilled. My career has already gone much further than I would have imagined,' she says.

So where next?

'Hopefully some new challenge within Alcoa. I'm not saying I have learnt everything I should know as a CFO; there's always more. But I would like to think that maybe I could branch out maybe back in Asia.'