Robert Black is both Scotland's watchdog-in-chief and something of a paradox. He is the single most important person in a position to scrutinise the democratic workings of the Scottish Executive - but his own selection had nothing democratic about it. He was appointed by the crown five years ago, giving him security of tenure to stay in the job for as long as he himself sees fit.

Black is the man who is sought out to provide the definitive judgement when policy goes pear-shaped - whether it is the Reliance prisoner escort contract, the Holyrood building project or allegations of mismanagement at Scottish Enterprise.

And that is just when he is on emergency duty. Most of his more routine work involves picking his targets before others do, which he does without any evident fear of controversy.

One reason for his increasing profile is that the parliament and its media pack have given much more attention to watchdog findings than was possible before devolution. When Robert Black pronounces on an area of government policy, public officials pay attention, because his findings have teeth and he gets noticed. That should be evident this Thursday when he delivers his findings on bowel cancer care, one of the main pillars of Executive health policy.

Another reason is that Robert Black appears to be the very personification of integrity. Banff-born and Aberdeen-raised, the 58-year-old is one of those Scottish civil servants with a quiet passion for public duty. Appearing austere but with a quiet charm, and keeping his distance from the subjects of his auditing, he is much more than a bean-counter. Indeed, he isn't a bean-counter at all, lacking formal financial qualifications.

His background instead is as an Aberdeen economics graduate turned social policy researcher at Strathclyde Regional Council, from where he rose to chief executive roles at Tayside Region, and before that Stirling District Council in the late 1980s.

There, he noted one Jack McConnell as a councillor on the rise: "You could see Jack had a lot of ability, " he recalls.

"He was a young man with a very astute political mind."

That background explains how Black approached his newly-created job when he took it on five years ago, heading Audit Scotland and using its 260 staff to draw together the watchdog functions for much of Scotland's public sector. His turf does not extend to councils, however. They are covered by the Accounts Commission, though with a growing amount of overlap.

He observes that the previous regime "lacked ambition".

"It tended to concentrate simply on the financial numbers, the beancounting. It was very slow, so it took far too long for the result to come out."The stress now is on checking the quality and efficiency of public service delivery when set against the starting objectives. That has meant auditors in the unaccustomed role of asking, for instance, what hospital patients think of the food provided for them.

"There's been a huge challenge for quite a lot of the longer-serving staff to change to a new culture of delivery, " he says.

Among the staff who work with Audit Scotland there is a wider range of skills and high quality people being attracted, he says.

"It has been an extremely intense few years, combining the chief executive role with the role of auditor general, taking a judgement on the issues that come across my desk.

"I enjoy it. It's great fun. I've always had a passionate interest in good public sector management and this role gives me a unique and privileged insight into how public services are delivered."

He continues: "The audit of the financial statements is a part of the core business, but the standards of financial management in the Scottish public sector are high, so I don't see that as a major strategic issue in Scotland. I'm motivated by trying to drive up the quality of public service delivery, because if it's not impacting on the client, the user, the patient, then what's it all about?"

There are those who wonder at a system which allows him to look at policies and projects only after they have begun to go wrong. The McCrone pay and conditions deal for teachers, for instance, is only now getting the Robert Black treatment, five years after it was struck and began to be rolled out.

Should he be able to act sooner? The rules require that he cannot make judgments on policy before it is set and implemented, he explains. "If I could stop things happening before they happen, in effect I would be a dictator in Scotland with a power of veto, and I'm not elected.

Everything has to be retrospective. But we try to make the audit as real-time as possible, so that we can learn lessons."

The McCrone deal will be one of the areas to be tackled in a programme for the next 12 months which ought also to make ministers pretty nervous. He is looking across the full range of departments to assess whether they are working adequately together on transport, and suggests MSPs should be doing likewise.

He is also looking into the Executive's penchant for initiatives and pilots, to see if they are getting value for money or merely raising the headline count. And he is looking to do a joint report with his English counterpart, to see how the Scottish and English approaches to health service problems are delivering results.

That is likely to build on his criticism of "weak" NHS statistics, which make it difficult for him or anyone else to register progress, or lack of it. He argues that the Executive and the national debate about the future of the health service need to get upto-date in their understanding of the extent of what the NHS does, measuring how effective it is at treating people in their own homes and in the community, as much as measuring hospital waiting times and lists.

The study is also likely to look into concerns about recent pay deals. "A lot of money is going into the health service, primarily into pay deals for consultants, for GPs and other staff, without real clarity about benefits for the service and for patients and what we're going to get as a result of that."

Of course, the auditor general's highest profile task has been investigating the Holyrood building project. It was one of the first jobs he took on after his appointment, requiring him very quickly to demonstrate his independence.

He disappointed some by declining to blame any one person or group, while carefully explaining why so many aspects of the procurement went wrong and compounded the early mistakes.

However, he also came under criticism over a decision not to release the report of an independent cost consultant that he had commissioned to help his inquiry.

He says now that he would make the same decision again, as his job is to provide the fullest possible picture and that the Gardiner and Theobald report was only looking into a limited part of the story. But now freedom of information legislation would require him to release such a report upon request in any case - as has happened with that report.

The reason for Robert Black's increased impact on Scottish public life lies also with the work of MSPs, who take on his findings as the basis for much of their scrutiny of ministers and officialdom. He rates highly the work of Holyrood's audit committee, which has as its only task the consideration of the auditor general's reports, with followup hearings to interrogate civil servants.

He is less positive about the role of other committees, including finance, saying its performance has been patchy, and that it has not done enough to get on top of the budget process. To that end, Black believes MSPs could do with training to help them through the complexities of the public finances: "The Scottish parliament is still starting out on a journey and I do think a lot more could be done to make the scrutiny procedures of the parliament work better. It's important that MSPs are offered the opportunities to build their knowledge of how government works in Scotland, and that includes finance.

Government is a huge, complex business, and the pressure on MSPs' time is so enormous that anything we can do to help them with courses that develop their understanding and knowledge then the better."

He is, however, much too canny to comment on the effectiveness of MSPs in holding ministers to account in parliament.

And he shies even further from the question of how MSPs can be held to account, to see if they provide value for money.

The work of the auditor general is based on what the objectives of policy were when it was formulated, then comparing and contrasting with how well public servants perform against those stated objectives.

Robert Black is not one to know what voters had in mind when they chose their politicians. So he is leaving it up to us, the voters, to do our own auditing on that score.