No one who was present on the day of the publication of the Scott Report into the arms-to-Iraq scandal nor the debate which followed can ever forget his mastery of the detail of the report and his ruthless exploitation of the weaknesses of the government position. If you needed an advertisement for the virtues of adversarial politics, Robin Cook provided it.
He and I had agreed to co-operate over Scott, and as we toured the studios in the company of Malcolm Rifkind - who was gamely trying to put the government case - our party press officers were engaged in an extended and unresolved discussion about when Labour and the Lib Dems should hold their separate press conferences on the following day. Robin Cook took me aside eventually and said why don't we have a joint press conference, an idea which no doubt seemed a heresy to the press officers but which appealed to me. I needed the authority of Paddy Ashdown before I could agree. When I said this and asked Robin Cook if he had to seek the same from his own leader Tony Blair, he looked rather surprised and said flatly, "No"'. The press conference duly took place and was an early and very public illustration of Labour and Lib-Dem co-operation.
Robin Cook was delighted by the Foreign Office but I have no doubt that he found government more testing than opposition. His assertion that Labour's foreign policy should have an "ethical dimension'' and have the promotion of human rights as its centrepiece echoed what his party (and my own) had been saying in opposition. The reality proved to be more difficult for him.
By 2001 Robin Cook seemed to have the measure of the Foreign Office, better able to navigate the dangerous shoals of the Middle East and the equally hazardous waters of the Asian subcontinent. But his handling of Sierra Leone was by no means deft and of that the full story has yet to be told.
He expected to go on at the Foreign Office after the election of 2001. The decision that he would not be offered that opportunity came out of the blue. It is no secret that he thought long and hard about accepting the post of Leader of the House which was, and was seen by him, as a demotion.
But he came to that most parliamentary of responsibilities as if it was all he had ever wanted to do. He had an agenda for reform of the Commons and Lords which went beyond working hours and abolishing the principle of heredity. Those four parties who worked with him paid tribute to his open-mindedness and his sense of responsibility towards Parliament and not just to the Government or the Labour Party.
Iraq changed all that. His resignation speech was a masterpiece, but those who watched carefully saw him surreptitiously brush away a tear as he sat down. To argue within the Labour Party was one thing but to argue with his party from the outside and to resign from its government was a deeply emotional step for him to take.
Scotland is a political village. Scottish MPs know each other from school and from university and there are friendships across political boundaries. Sometimes these are warmer than relations within the parties themselves. In private Robin Cook was warm, witty and self-deprecating. He could trade political gossip with the best of us. He had a hinterland of racing and the outdoors. He was an accomplished columnist in national newspapers. He could see a joke and he could crack one. The reality of the man was a long way from the perception. Irrespective of party I have lost a friend and a frequent political ally. Public life is gravely diminished by his passing but so too are those who knew him.
Menzies Campbell is deputy leader of the Liberal Democrats