When the full history of Britain's handling of its crisis over bovine spongiform encephalopathy — BSE, or ‘mad cow disease’ — comes to be written, the transcript of the current inquiry being held under Justice Phillips will be a key text. And few passages of that transcript are likely to be as rich, particularly as an illustration of the highly complex relationship between science and politics, as last week's evidence by former and current members of the Spongiform Encephalopathy Advisory Committee (see page 490).

The committee was set up in 1990 on the recommendation of an earlier inquiry headed by Sir Richard Southwood, formerly professor of zoology at the University of Oxford. Its remit was a sensible and desirable one — or, at least, it appeared that way at the time: namely, to keep an eye on what was known and what was not known scientifically about the nature of BSE, how it was spreading among British beef herds, and its possible implications. In particular, these included the likelihood, previously described by the Southwood committee as “remote”, that BSE could spread from cattle to humans.

In practice, this remit appears to have been impossible to meet. Politicians and government officials, under intense pressure to provide statements that could be used as public justification of a particular course of action (or, just as frequently, inaction), perhaps inevitably sought to draw on the conclusions of a group of scientific experts who could be held to be independent. Most notable was when John Gummer, the minister of agriculture at the time, invoked the name of David Tyrrell, then chair of the committee, when he stated that “What Tyrrell says, I will do”.

It will be up to Phillips, whose inquiry is due to finish at the end of the year, to determine whether a crucial mark was overstepped in compromising the responsibility of a committee whose original brief was restricted to science alone. The present evidence indicates that this did indeed happen, although the full response from the civil servants and others involved is yet to be known. What is already clear, however, is that the inquiry has revealed the need for a much sharper definition of the role of science advisers in policy making.

The publication and propagation of guidelines on just this topic by Sir Robert May, the government's chief scientist, is an important step in the right direction. Even these, however, appear to argue for maintaining a sharp distinction between the scientific and the political. One of the key questions that the Phillips inquiry needs to answer is whether this distinction remains realistic in such sensitive (and scientifically uncertain) fields as BSE and its relationship to Creutzfeldt-Jakob disease, or whether new formulations can be imagined. Providing firm guidance on this alone will turn out to be a valuable contribution to modern politics.