Fiona Logan is not someone who spends time twiddling her thumbs.

"I always just feel that sleep's a bit of a pain because there's so much to do in life you just don't have time to sleep," she says, as we chat in the conference room of the organisation she runs, Loch Lomond and The Trossachs National Park, as the spring rain beats down on the plate glass windows.

"When you just think about all the historic buildings you'd like to see, all the plays, how can we have time to sleep?" She smiles. "I'm a bit like that, probably annoyingly so."

It explains why she is so busy. This is the first time she has had an hour to chat in three weeks; her diary for the next month is choc-a-bloc. As a single mum of two with a demanding long-hours job and a dog that needs to be walked, there is not a lot of down time in Logan's life, and even if there were, she would not spend it watching telly.

This energetic nature has stood her in good stead as chief executive of the national park, a position she has held for six years. Logan, 42, had no public sector experience before being appointed. After a technology and business studies degree at Strathclyde University, she was one of a few out of 60,000 applicants to win coveted places on the Unilever graduate trainee course.

She then spent ten years in New Zealand working for Unilever, IBM and Greenpeace, before returning to Scotland to run a management consultancy business with her husband, a job that fitted in with parenting two children.

When her marriage broke down, she decided it was time to find a job where she and her ex were not working together, good friends as they are, and a friend drew her attention to the national park post. "I thought, public sector? National parks? I was really sceptical about it until I phoned Bill Morton, the interim chief executive, and we just clicked.

"Obviously I had my environmental credentials and a huge amount of business experience and there was a huge change role needed here, and I think that's what Mike Cantlay [then the park authority convenor] saw. I was really fortunate."

The park, which came into being in 2002, covers 720 square miles, 21 munros, 22 lochs, 50 rivers and large burns, and Britain's largest area of fresh water (the 24-mile long Loch Lomond). It gets four million visitors a year. The authority is based in an award-winning environmentally friendly building in Balloch and has responsibility for planning, sustainable management of the natural heritage, promoting the park to visitors and enabling sustainable economic development.

While Logan stresses the importance of continuity, she says the way things are done has changed "a huge amount" since 2008. The park had taken on a very wide range of responsibilities in its infancy, but by 2008 was entering a new phase when more focus was required. That is what Logan, with her private sector background, feels she was able to bring.

"We have significantly changed stuff for the better and it's absolutely not been about me. You could pick any planner, ranger or conservation person out of this organisation and they would be as passionate."

Logan is thrilled by the feedback she gets about how responsive the authority is to local people.

She does not live in wellies, because much of her daily job is about reports and spreadsheets, but she does bring to the role a lifelong love of the outdoors. Born in Montreal where her parents were both teaching, she came to Scotland aged two and spent her childhood in the village of Newport, Fife, where her parents still live. Much of her childhood was spent in the open air, cycling everywhere, playing tennis five times a week, and going on regular hillwalks with her parents and younger brother Brian. She loved school, first the local primary and then Madras College in St Andrews. Does that mean she was a high achiever?

"Absolutely not," she snorts. "I spent some time standing outside doors when I was at secondary school, for talking too much." She pauses, then laughs. "I'm curious, I love people and I ask questions, and I think at school that enthusiasm came across as annoying, to certain teachers."

At Strathclyde, she came into her own academically and threw herself both into her degree and her social life, joining the ski club and becoming president of her hall of residence, which is how she met her future husband Paul. It impressed the recruiters from Unilever. After a year out after university teaching skiing in Switzerland and canoeing in the Ardeche, she started with them at Port Sunlight in Merseyside, the firm's historic home.

After just over 12 months there, however, she asked to be transferred to the firm's training scheme in Australasia because Paul had just been posted there. They agreed. Her training continued but she eventually found herself in the team of a man who "really chipped away at my confidence" and after she had reached the grade she wanted, decided to leave. That was when she came across a vacancy at Greenpeace.

Going from the heart of the blue chip establishment to the world of rebellion and protest was quite a leap, and Logan admits she did not make the decision lightly, but it was 1995, the tenth anniversary of the bombing of the Rainbow Warrior protest vessel by French intelligence agents, an incident in which a protester was killed. The anniversary was creating a buzz in the group's native New Zealand, which appealed to her.

She was not new to demonstrations in any case, having been "a big animal libber" at university.

In her new role as a fundraiser, she did her bit holding banners and chanting, including once under the tense gaze of US snipers when the then US Secretary of State Madeleine Albright was in town, but she also threw herself into the fundraising. Boosted by the anniversary and Logan's decision to push new forms of subscription, the organisation tripled its income.

But then it was back into the corporate world, this time with IBM. Though she loved the job, becoming marketing director, she hit the pause button on her corporate career when she became pregnant and realised the travelling she was doing - all over Asia - was not compatible with parenthood. She left IBM to work with Paul, by then her husband, on a management consultancy business - not that it meant slacking up at all: "I was in the hospital in labour and was typing stuff into our database to get mailers out for a seminar we were having. But I had a great nanny from day one and saw heaps of the kids."

After having their first child, the couple returned to Scotland and continued to run their business together until Logan's move into the public sector. One of her aims has been to reduce the park's reliance on public funding.

"We have been for the last five years exploring a more commercial approach for delivering our services because I think that's what the taxpayer demands of us, to be effective and efficient with the pretty limited funds we are given. I take that duty very, very seriously.

Are there frustrations in the job? "Absolutely," she admits laughing. "Oh yes. We work with I don't know how many partners, from big national bodies to four much much bigger local authorities, to NGOs.

"They are all driven by their own priorities, they don't always do what we want them to do."

And when she is not working, she is "kept in the present" by her children Calum and Kyla, now 10 and seven. "I've got a superb nanny, she's like a second mum to my kids," she says.

Will she stay in the public sector? She pauses. "The answer is I don't know," she says.

"I just think I will always do things I'm passionate about. However, the journey at the park is far from over."