WHERE quango meets civil service meets political administration is a foggy area, hard for outsiders to penetrate. Scottish public sector Kremlinologists are having a speculative field day with the surprise appointment of Lena Wilson - already Scottish Enterprise's chief operating officer - to head inward investment agency Scottish Development International (SDI). Given the new government's international ambitions, this crucial, world-facing role more than consolidates Lena Wilson as one of the most powerful unelected public figures in Scotland.

Wilson, 44, had been straddling the SDI brief since last September, following the departure of predecessor Martin Togneri. Why did it take so long for ministers to formalise this arrangement? Had she angled for the dual position all along? Or did she have to be persuaded to save a fat public sector salary in a shrinking operation? Was the job previously promised to a pro-SNP business star or mandarin? And why was news of her appointment slipped out on a Friday afternoon?

Scottish Enterprise insists that there is no mystery. The government interviewed external and internal candidates before realising that the right person was the one already coping with the multi-timezone, globetrotting SDI job while juggling the most drastic restructuring in the history of the enterprise network.

SE had lost some of its grassroots functions in the "re-focus", and Wilson had already remodelled management structures to allow more delegation. There was a good case for combining SE and SDI leadership roles, and she had the international experience, contacts and bureaucratic infighting skills that were not available elsewhere. It was a case building a structure around the available talent, an admirably pragmatic approach. A similar thing happened in 2005 when SE boss Jack Perry created the chief operating officer post to accommodate her talents.

In the managerial register that is SE's lingua franca, Wilson is characteristically gung-ho about her role: "I've put in place some more effective management solutions beneath me, to take up some of the slack in the tactical things to allow me to align the strategic job across the piece.

"I'm quite an organised person, thankfully, and I've always been able to assimilate a lot of tasks. The thing for me is sticking to the priorities and leading the team globally, aligning what SDI is with the SE account management process as well as the government's strategy."

Given some of the adverse publicity about her salary and pension, she is uncomfortable discussing her non-work self, let alone talking about the inner workings of the development bureaucracy. Her ability to stay impenetrably on-message is viewed with awe by colleagues.

This is how it should be. Wilson is paid to be relentlessly focused on the strategic aim of growing Scottish business and presenting Scotland as an attractive investment destination. She has learned that the Scottish press, like Hannibal Lecter,, like Hannibal Lecter,should be given nothing that could be fashioned into an offensive weapon. Or which could distract attention from the strategic script.

"Lena plays her cards very close to her chest," says one colleague and admirer who has followed her meteoric rise through this highly complex and competitive public organisation.

"She has a very strong pubic persona, but there is a lot that she doesn't give away. It's hard to know what she is up to."

All that matters about what she is "up to" of course, are results for Scotland plc. These are impressive, last year especially so given the drastic internal upheavals and the hostile economic environment. SDI managed to attract more than its target figure of inward investment jobs last year, and in March Scotland beat 38 other regions to be named as European Region of the Future.

Her appointment has gone down well with the business lobby, which sees her as a supreme, small-p political operator of the type that makes things happen. "I have been very heartened by the positive response to my appointment from the business community," she says. "It's a testament to the kind of relationships you try to build up over your career."

Ultra-competent and industrious, Wilson is also known for her motivational abilities. She is quick to praise and to pass on praise. "Lena is good for morale," says one underling.

Like Robert Crawford, her former boss and mentor, who brought her back to Scottish Enterprise from the World Bank, her story is one of iron self-discipline and drive, rising from a "very working-class, hard-working and inspirational family", which migrated from Partick in Glasgow to East Kilbride. She studied for a BA in public administration at Glasgow Caledonian, followed by an MBA from Strathclyde University.

Her early career was spent in production and quality management in the electronics industry, before she joined the Scottish Development Agency (forerunner of Scottish Enterprise) as part of their management development programme.

She spent five years in the inward investment agency Locate in Scotland, precursor to SDI, before joining Scottish Enterprise Forth Valley in 1994, rising to deputy chief executive in 1996.

From there she was seconded to the World Bank in 1998 for two years as an investment advisor to the Multilateral Investment Guarantee Agency, working in Latin America, Africa and Asia advising governments on conditions necessary for attracting foreign direct investment.

Returning to Scottish Enterprise in 2000 as senior director of customer relations, she was appointed chief operating officer just as the network was coming under heavy press attack. Much of it was stoked by the SNP, which came to power promising a radical overhaul of the network.

A survivor as well as a thriver, Wilson has made a virtue of a traumatic period of change, claiming that it has allowed better strategic alignment between growing businesses and helping them to internationalise through SDI. But when the goals of the previous administration and this one are so radically different.Scotland has always competed for inward investment with other parts of the UK, but now she is effectively a roving ambassador for an aspirant independent nation. The nuances of her discussions with ministers about Scotland's message to the world make for speculation.

As a public servant Wilson's own political views are strictly her own business, but she is careful to underplay differences between her previous Unionist masters and her current pro-independence ones.

"I have always talked about Scotland's uniqueness and tried to separate us from the rest of the UK in that regard, to present us as a high-value, business-friendly destination.

"For me, nothing has changed in wanting to maximise the amount of foreign investment in Scotland and to help as many Scottish companies as possible to internationalise," Wilson says.

How well she achieves that ambition is what she will be judged on, but her confidence that she can do it is infectious.