The scholar who in my lifetime has most boldly and confidently stated the importance in an open society of the links between intellectuals and government is Edward Shils. Writing in 1972, the great American sociologist and Anglophile declared: "intellectuals are indispensable to any society ... and the more complex the society, the more indispensable they are. An effective collaboration between intellectuals and the authorities which govern society is a requirement for order and continuity in public life for the integration of the wider reaches of the laity into society."

This function is very hard to carry out because the terrain I think Shils was marking out lies between the quick burst of verbal analysis on Newsnight and the kind of written works the research assessment exercise requires us to produce. It is the thoughtful running commentary on a series of vexing and interrelated current problems with their tangled roots in the past which is so necessary but so difficult to provide.

The rash of new think tanks does its best. But, like all entrepreneurs searching for a niche and competing in a market they involve an element of rashness, a dash of the new rather than the true. The more orthodox parts of the universities cannot do it either unless they succumb to the temptation of contract work and neglect their core business - scholarly research and its transmission through teaching and writing.

Yet I know one glowing exception of high and immediate utility to Government, Parliament, the press and the public which is within the university perimeter, has a fine track-record and, paradoxically, is on the kind of financial knife-edge which makes survival problematic. It is the Constitution Unit housed in the School of Public Policy at University College, London.

It was founded in 1995 to do the research and development an incoming government would need if it were serious about the wide- ranging reform in both the rules-of-the-political-game and the kind of substantial institution- building that might accompany it. The Blair government has shown itself to be so and the seven substantial reports and 12 Briefings the unit produced in its first two years has, I know without question, proved invaluable to the civil servants in the Cabinet Office's Constitution Secretariat which was quickly constructed in May and to the ministers on the battery of constitutional Cabinet Committees which have been in session since then.

The Constitution Unit is now down to its Director, Robert Hazell (ex- Home Office and Nuffield Foundation), and one assistant with just enough funds for it to reach next spring on a shoestring. Like several of my friends among the heavy-duty end of current affairs journalism, I am, for selfish reasons, very jumpy about the possibility of the Unit's demise. I live off its products in the lecture hall and in the seminar room as do the journalists in their columns.

More important still perhaps, Whitehall and Westminster need a running commentary of the quality that only the unit has so far provided on a constant basis. They need it as the complicated, interlocking mechanics of constitutional reform are pieced together over a period that will stretch way beyond next spring as the devolution bills are published, the commission on the electoral system begins to deliberate and draft legislation on freedom of information, incorporation of the European Convention on Human Rights and Lords reform are promulgated.

Business needs such a service too. Chief executives tell me so. The best of the private sectors' public-affairs divisions find this a puzzling area (which it is) where the end-game is unpredictable. All that is needed is some pounds 120,000 a year. If I was a chief executive I'd reach for the chequebook now. But on a professor's salary ...

The writer is Professor of Contemporary History at Queen Mary and Westfield College, University of London