Why was David Nutt sacked?
It is the question that is buzzing around the scientific community tonight - why exactly did the home secretary ask his most senior drugs adviser to pack his bags?
Alan Johnson said today it was because Professor David Nutt had been "lobbying" against government drugs policy. But the former chair of the Advisory Council on Misuse of Drugs says that all he was doing was publicising scientific research into the relative harms of illegal drug use and other pursuits.
So where exactly is the line that was crossed?
The Home Office was offering no help on this tonight, other than to refer me to the letter that Alan Johnson sent Professor Nutt asking him to stand down (see my previous posts, Nutt faces sack and Nutt gets the sack).
In it, the home secretary states that "it is not the job of the chair of the Government's advisory council to comment or initiate a public debate on the policy framework for drugs".
In other words, the minister sees the relationship between his scientific advisers and his department as, essentially, a private one: you tell us about the "matters of evidence", as he describes them in his letter, and then shut up.
Professor Nutt, and I think many other scientific advisers to government, would question whether the relationship is quite that servile. Indeed, some argue that scientists have a responsibility to inform and educate the public about risk - even if ministers don't respond to their advice.
The BSE disaster in the 1980s and 90s is a case in point: some advisers and government-employed scientists said they told ministers that they feared the disease in cows could spread to humans - warnings that were not published nor heeded until it was too late.
The science did not fit in with the Ministry of Agriculture's policy that British beef was entirely safe. Remember John Gummer trying to shove that burger into his daughter's mouth outside Parliament in 1990?
Advice about BSE was, of course, advice on risk - just as the Advisory Council on the Misuse of Drugs offers expertise on the relative risks of different illegal drugs. After the huge inquest that followed, the official BSE Inquiry report had something to say on the relationship that should exist between ministers and a Scientific Advisory committee.
The inquiry concluded that "scientific investigation of risk should be open and transparent" and that "the advice and the reasoning of advisory committees should be made public". Without such openness, it was said, people would not believe government.
What some scientific advisers are telling me is that they are anxious that this is almost the opposite to what Alan Johnson is currently arguing. Far from using independent experts to "lend credibility to public pronouncements about risk" (in the ACMD's case, the risk from illegal drugs), the home secretary wants them to stay silent because "it is important that the government's messages on drugs are clear and as an adviser you do nothing to undermine public understanding of them".
The two resignations today suggest Professor Nutt's sacking may prove to be an important moment in the relationship between government and the experts who advise it. It almost feels as though a campaign is beginning, academics rallying behind banners calling for a restatement of the principles of the Age of Enlightenment!
An interesting recruit to the cause is Sir David King, the former Chief Scientific Adviser to the government who on Friday went public to support the home secretary because he thought that Professor Nutt had "crossed the line". However, on the Today programme the following morning, having read the letter demanding the professor clear his desk, he had changed his tune.
"When you hear the reasons that Alan Johnson is saying that he asked David to resign, I have much less sympathy. The reasons he is giving are effectively saying, it seems to me, he shouldn't put advice in the public domain. Absolutely wrong."
Sir David also referred back to the BSE crisis and said that it had "undermined scientific advice within government precisely because the scientists were seen to be muzzled by the politicians". Trust in advice had only been restored, he said, "because we have been seen to be putting it into the public domain".
This is an argument that has implications for every scientist and academic who provides research or advice for government ministers - and they have been talking about little else for the last two days.
They want clarification and reassurance. Where is the line that David Nutt is supposed to have crossed? Is it wrong to publicise scientific advice if it contradicts government policy?
There is also a question about the role of the ACMD. As I revealed here last year, the then Home Secretary Jacqui Smith had decided against reclassifying ecstasy before she had taken delivery of the council's report. What is the point of scientists giving up their own time to conduct years of painstaking and detailed analysis if ministers are not going to take any notice?
I expect the ACMD's next schedule meeting on 10 November may see the remaining members of the council asking for written assurances from the home secretary as to how government sees their role. If they are not content with his replies, the future of the committee would be in doubt and the whole relationship between government ministers and scientific advisers thrown into question.