He criticises the US government, for instance. Nothing like this was heard from William Hague, nor from Ian Duncan Smith nor from Michael Howard. Why on earth not? As Mr Clarke says, US Presidents are not always right and a true friend is a candid friend. And candidly, he remarks, US military tactics are "alienating" moderate Iraqi opinion. The US operation in Fallujah was "disastrous". And flying captives to some third country where they can be tortured - a policy known as extraordinary rendition - is an outrage.
You will wait until hell freezes over, of course, before you hear anything like this from Mr Blair, the Prime Minister. Nor is there any evidence from the numerous accounts of Mr Blair's dealings with the US president that he utters the slightest criticism in private. Mr Clarke's Tory rivals are similarly inhibited by the fact that most of them, unlike him, backed the Iraq war.
Mr Clarke also has a good go at deconstructing Gordon Brown's long period as Chancellor of the Exchequer. Britain has dropped from fourth to eleventh place in terms of international competitiveness. The tax burden has risen. By 2009 on current plans, it will be at its highest level for 24 years. No wonder, he says, "Gordon has spent the last three years desperately trying to get out of No 11 and into No 10".
After the knockabout stuff come Mr Clarke's policy proposals. In their way they are as radical as Mr Brown's early decision to give the Bank of England its independence. He would, for instance, remove the Treasury from the business of doing its own economic forecasts so that they would no longer be subject to political pressure. This is the same case that Mr Brown made for giving up control of interest rates. Instead Mr Clarke would give the job to outside bodies that were independent of the government. In the same vein, he would also establish a "truly independent statistics body".
If these two measures transfer tasks away from government, another of Mr Clarke's proposals would get rid of an activity altogether: He would abolish the Department of Trade and Industry. He admits that this would upset the panjandrums of the business establishment but "if we no longer have nationalised industries, we no longer need a department to run them. I do not believe that the DTI has made a substantial contribution to our national prosperity in its 35 years of existence". Refreshing stuff.
Most important of all, Mr Clarke argues that we cannot continue with Mr Blair's autocratic style. I quote the relevant passages in full. "We must sweep away the trappings of presidential government," said Mr Clarke. "The Prime Minister's department that Mr Blair has created in Downing Street must be dismantled. The Cabinet Office and not the Prime Minister's office should provide the co-ordinating machinery for government."
The status of the senior civil service should be restored. That means giving the Cabinet Secretary back his role as the Prime Minister's most senior adviser. Special advisers should no longer be able to direct civil servants. And listen to this: "As Prime Minister, I would make myself more receptive to the advice of an independent civil service and more accountable to Parliament. There are not many people who would put such constraints on their own power on taking office but I think it is important for the future health of British democracy."
Much as I applaud Mr Clarke's commitment, it would require iron determination. For the trend towards presidential style government began with Mrs Thatcher. It wasn't invented by Mr Blair.
Even Mr Clarke omits to say anything about the concept of Cabinet responsibility or about the status of cabinet ministers. In the pre-Thatcher/Blair system of government, cabinet ministers brought fully worked out policy proposals to the cabinet table. Only when they had passed this scrutiny would they become the responsibility of the whole Cabinet. Today, in sharp contrast, Mr Blair's cabinet ministers are like branch managers with very little power of their own.
The merits of the old system were that policy was better thought out and that power was dispersed. Now we have "New Labour: new tyranny". If Mr Clarke were elected Conservative Party leader and became Prime Minister and then governed as first among equals rather than as president - an unlikely series of events, alas - then he would deserve to have his statue placed on a plinth in Whitehall.