Some time this summer or autumn the Commission that bears his name – which has been asked to review the 10 years of devolution and recommend a new way forward – will have to deliver just such a diagnosis. Calman has so far sat through more than 50 evidence sessions, read 300 major submissions and sifted through hundreds of questionnaires. Sources close to the body say it is likely to back, overall, a strengthened Holyrood Parliament with more financial powers.
The task facing Calman is immense: to try to pick his way through a political minefield and come up with a solution which will stand up to fierce scrutiny.
Calman, who lives in the West End of Glasgow, is one of Britain's most distinguished doctors. He holds the remarkable achievement of having been chief medical officer both in Scotland and in England, advising the Government during the BSE crisis. Now the 67-year-old is both Chancellor of Glasgow University and president of the British Medical Association. He spends his spare time working on a collection of sundials and medical cartoons.
Wandering around Scotland listening to the views of the Scottish public over the past few months has been a pleasure, he says. "We're all reasonable people and Scotland is a place with a lot of reasonable people. We think hard about things and I think that is what we should do. There are ways of talking through these issues and finding solutions."
He is acutely aware that the Scottish constitution and its reform are not exactly the talk of the Clapham omnibus. "I was coming in this morning on the bus and there was this nice wee lady there, talking about how great these bus passes (for pensioners] are. We had a nice chat. And I thought to myself, 'I'll just test her on asymmetric devolution and full fiscal autonomy'. She wouldn't have understood a word of it, quite rightly. We've got to help them to understand a bit of this."
Calman's findings may not be the talk of the Steamie just yet, but that won't last for long. If, as many expect, his report recommends that large chunks of Scotland's tax revenue raising powers are sent to Edinburgh, it is highly likely that they will be enacted, as all three of Scotland's Unionist parties – Labour, the Tories and the Lib Dems – are signed up to it, both in Scotland and at Westminster. While the SNP's hopes of both holding and then winning a referendum on independence are uncertain, it is easy to see Calman's reforms being introduced post haste.
Ever the cautious doctor, Calman says his Commission has still to reach a conclusion. The big questions – should Holyrood get more financial powers? If so, by what means? – are still to be answered. "It's like dealing with a difficult clinical problem. You don't have all the answers, there's some uncertainty, you'd like to do a few more tests and you need to come to a decision at some point and you need to be able to communicate that decision to the nice person in front of you. That's what medical practice is all about; it's about listening. We have to listen to that and come to a conclusion."
With regard to a new financial settlement, that is proving a difficult task, he admits. "There is no model out there which you can just bring in. We've looked at Australia, at the Basque country, at Canada – and there isn't one we can just bring in… I don't know the answer yet," he admits. But come to a conclusion he will, he promises. "What we are aiming to do is to find a workable model which will suit the needs of Scotland."
He only wishes, he says, that the Scottish Government would give its own input. Calman read comments by First Minister Alex Salmond in last week's Scotland on Sunday, slamming the Commission for failing to rule out taking powers back from Holyrood to Westminster. "It would be slightly better if he came and talked to us," says Calman. "That would be quite handy."
Calman says he could arrange something "at the drop of a hat". The Scottish Government points out that it has already written to the Commission, supporting its case to get more borrowing powers. But Calman would like to see Salmond in person.
"We've had a paper from John Swinney on borrowing powers but no contact… we have tried a lot of times and written a lot of times and we don't get a lot back. Obviously, they have a particular view in mind – independence – but they have this great opportunity of influencing the way in which Scotland operates through the Scottish Parliament that they are just missing."
He adds: "I suspect that is partly because when the report goes out eventually they can say, they didn't ask us about it. They can say, that's nothing to do with us guv, and they can criticise it all the way through. We certainly expect that."
Recent minutes from the Commission show that there is significant irritation at the fact that Salmond has now met with the Welsh body. "The Commission noted with regret that whilst the First Minister had met members of the Holtham Commission, he had still not agreed to meet the Chairman or provided evidence to the Commission," they record.
Calman is too diplomatic to discuss this on tape, but he does have a little dig at the SNP Government's web-based 'National Conversation' forum. "I don't think the National Conversation (the Scottish Government's web-based forum on independence] has got very far. This is the only game that there is in town right now and it is a great pity that they are not taking that opportunity," he declares.
He goes on: "We need open minds to be able to test these things and debate them. My views have shifted as we've discussed these issues."
Only a non-politician would admit so candidly to having changed his mind like that. The country must hope that when he decides one way or the other, the treatment will be worth it.