Geoff hoon ultimately took the decision to release David Kelly's name outside Whitehall, an e-mail submitted to the Hutton inquiry at the last moment confirmed yesterday.
It underlined the Defence Secretary's personal responsibility for identifying the weapons expert in a letter to Gavyn Davies, the BBC chairman, as Andrew Gilligan's suspected source.
Mr Hoon was acting on a suggestion from Jonathan Powell, Tony Blair's chief of staff. The e-mail, sent at 10.24am on 9 July, was from Peter Watkins, Mr Hoon's private secretary, to Kate Wilson, the chief press officer at the Ministry of Defence.
It read: "Kate. We spoke. Herewith draft letter to Gavyn Davies. Is this consistent with the Campbell suggestion this morning? JP [Jonathan Powell] has separately suggested to SoS [Secretary of State, Mr Hoon] that we should simply name our man, but left the decision to Mr Hoon, who has not yet reached a final view."
Mr Hoon named Dr Kelly when he wrote to Mr Davies for a second time on 9 July in the hope that the BBC would confirm that the scientist was Mr Gilligan's informant.
But both letters failed in their attempt to persuade the BBC to reveal the identity.
In his appearances before the inquiry, Mr Hoon has not taken full responsibility for the letter to the BBC chairman. He simply confirmed that the idea to name Dr Kelly in the letter came from Mr Powell after "some discussions between Downing Street and the Ministry of Defence" on its contents.
Earlier, a colleague of Dr Kelly broke down in the witness box as he described how the scientist asked him to accompany him to his appearance before the Commons Foreign Affairs Select Committee.
Patrick Lamb, the deputy head of proliferation and arms control at the Foreign Office, stumbled over his words as he recalled that he had previously not been sure of Dr Kelly's view of him. "This was the first occasion when it was clear he valued my opinion and had a certain respect for my judgement and would have appreciated my personal presence at the hearing," Mr Lamb said.
He said he had wanted to do everything possible to help Dr Kelly to prepare for an ordeal that was "analogous to any order he had experienced in the former Soviet Union or Iraq". But Mr Lamb stressed: "I had no inkling or foreknowledge of what would follow."