Sunshine streams through the windows of the wood-panelled room, where fellows of Brasenose College sit in armchairs behind newspapers.

But, at the far end, Professor Vernon Bogdanor is speaking with increasing exasperation about another historic institution, whose members have come to resent even occasional shafts of daylight.

“They live in what you might call ‘a house without windows’,” he said, warming to his theme. “They do not like to look outside to see how people are reacting.”

There was a time, not very long ago, when politicians would seek to discomfort senior common rooms like this at Oxford University by labelling dons as being out of touch in their medieval ivory towers. It is doubtful that many MPs — reputations battered by the expenses scandal — will be levelling such charges at anybody or anything for some time to come.

But in Brasenose College, there is a man who is uniquely well qualified to lecture our rulers on their scandalous behaviour, arrogance and greed.

The Professor of Government at Oxford University has long been regarded as England’s foremost expert on the British constitution. One of his favourite sayings is that he makes a living out of something that does not exist.

But that is a joke he may have to revise in the coming months and years, as politicians desperately scramble around for reforms to make Parliament more accountable in order to restore its dwindling authority with the public.

In fact, one of Prof Bogdanor’s former students at Brasenose College, David Cameron, has in recent weeks been making the running in setting out a programme of constitutional changes, designed to bring about a wide-ranging redistribution of power.

Of course, at 66, Prof Bogdanor has heard the arguments and seen no end of false political dawns before.

But this time he believes we are seeing something very different, with British politics entering uncharted territory. “I think the expenses crisis is a defining moment in British politics,” he said. “The traditional view in Britain of Parliament being sovereign and deciding itself what it does is no longer acceptable to the public.

“People no longer think it is enough to vote once every four or five years and let politicians get on with it.

“The traditional representative system rested on the MPs having authority. But if the public feel that they are not only no better than the rest of us, but perhaps a good deal worse than many of us, they have lost that authority. It is difficult to overestimate the deep-seated sense of public anger.”

On the face of it, Prof Bogdanor perhaps has even more reason to be furious with MPs than the rest of us. For the expenses scandal blew up as his new book called The British Constitution was going to press, with no chance to update it.

It is darkly ironic that having dedicated a lifetime to the subject of the British constitution, he has seen it take the whole grubby business of MPs’ expense practices to put it at the top of the political agenda, while stirring the public’s interest in changing the way we all are governed.

But Prof Bogdanor does not seem to be irritated in the slightest about the seemingly unfortunate timing. For he reckons the MPs’ abuses have merely served to bolster his argument that it is time to slice up power, with hefty chunks of it passed downwards.

In his view, the scandal has come after a decade of radical changes in the way we are governed, even if these great changes passed a good proportion of the population by. Reforms such as the Human Rights Act and devolution, together with British membership of the European Union, have seen one constitutional order, seemingly hallowed by time, replaced by another.

“The new constitution has had the effect of cutting power into pieces,” he said. “It has dispersed power. Yet this dispersal of power has hardly registered with the electorate and done little to counteract widespread disenchantment with politics.

“If you asked someone in Oxfordshire what difference all this has made, they would probably say ‘not a lot’. I don’t think they would want devolution. They might support the Human Rights Act, but would hope never to have to use it. ”

But the problem has been that power seems to have been distributed sideways to the judges, politicians in Edinburgh and Cardiff and Boris Johnson in London. It has not been redistributed to the ordinary voter, which is what Prof Bogdanor wants to see.

But the expenses scandal now means that everything is up for grabs.

“People are asking how MPs got away with it for so long? They are saying, ‘we need to have more control over our MPs’. Perhaps we should be able to recall MPs who behave badly. We should have more say in the choice of the local MP and perhaps more of them should be independent.”

The idea of primary elections, where ordinary people rather than small party groups elect candidates, and directly-elected mayors, are two ideas that attract him as part of a new order.

He also likes the idea of holding local referendums on big issues, to give local people the chance to have their say.

Direct democracy could take the form of five per cent of the local electorate being able to trigger a referendum on any given subject.

“It is an interesting innovation that we have already had in Oxford. There was a vote on whether Oxford should have a directly-elected mayor a few years ago. If five per cent of the population could require a referendum on that, well, why not on other local issues? Say, the way our schools are organised, or the organisation of the health service.

“People are saying we should have more control ourselves. Not just elites. There are all sorts of matters on which local people have strong views and should have their say. People are much more educated and articulate than they were say in the 1940s and 1950s, when people were simply grateful for anything they could get.

“Well, they are not grateful for anything they can get now.

“People are demanding a greater degree of political control of public services. They are encouraged to complain if the standards of services are not good enough. They are encouraged to be active consumers.

“But the political system still relies on citizens being passive, voting every four or five years and leaving everything to MPs. I think that is not acceptable any more. The expenses scandal has highlighted all that.”

Localism — the idea of giving more power, not only to local councils, but to local people themselves — he says is a catchword for the age. For, he believes it is local reforms — not the big, glamorous ones, like the reform of the House of Lords — that really concern people.

“Giving them more power to affect decisions about local services, schools and hospitals — that is what people most care about.”

But he says this would mean people should no longer simply blame the Government and complain about the fact that the standards of local services vary from area to area.

“You can’t complain of postcode lotteries if you have strong local government. It would be no use people then saying, ‘services in Buckinghamshire and Oxfordshire are not the same, what a scandal’.

“And you have to stop blaming the centre for things going wrong.

“If state schools in Oxfordshire are no good, you would have to blame your local authority.”

But he regrets that modern councils are now tightly organised along party lines, with councillors even less inclined to rebel than MPs, living under the lash of the party whips at Westminster.

“That is one of the reasons I favour elected mayors. You get more independently-minded people. Parish councils are one of the areas that must be considered for stronger powers.”

Given that he has acted as an adviser to a number of governments, including the Czech Republic, Hungary, Israel and Kosovo, whose constitution he helped draw up, I wondered whether his most famous politics student has been on the phone seeking his help?

Apparently not. But he is delighted that David Cameron is now so focused on constitutional matters, even if he marks down his former student for wanting to cut the number of MPs and for wanting fixed-term parliaments.

Prof Bogdanor also believes that Mr Cameron, like all the other political leaders, is merely responding to a debate that for once is being led by the voters.

“I do not think David Cameron would have made his important speech in Milton Keynes on the constitution, if not for the expenses scandal.”

His affection and admiration for Mr Cameron, the MP for Witney, are obvious. Those who continue to view Mr Cameron as a political lightweight from the world of public relations, or as a former Bullingdon Club champagne-quaffing Hooray Henry, simply do not have the measure of the man.

“He was one of the ablest students that I have ever taught. He got an outstanding first-class degree. He is extremely able and an extremely nice man.”

But is the Tory now drawing on his old professor’s radical ideas?

“Perhaps I contributed to his interest in these matters, but I’m not responsible for his views,” replies Prof Bogdanor. Happily, he is never short of a newspaper or television studio in which to set out his own positions, and is now established as one of Oxford’s most sought-after communicators.

The breaking of any new political scandal or anything from a royal divorce to police raids on MPs’ offices, invariably result in newsrooms clamouring for Prof Bogdanor’s expert opinion.

We can be certain that, like one of his best students, some busy times lie ahead of him.

But we can be equally sure the Oxford man whose views politicians and commentators want to hear will continue to press the case for ordinary people to have a greater say.