The Prime Minister led the tributes to the man whose resignation on the eve of war in Iraq almost brought him down. But as he and others acknowledged last night, it was a decision taken on principle and executed without rancour.
His brilliance as a parliamentarian, forensic investigative skills and tactical acumen were the main themes of accolades paid him from all quarters.
His legacy, said Mr Blair, would be that he had helped to redefine Britain's relationship with Europe, and had put human rights at the heart of foreign policy.
"Robin was an outstanding, extraordinary talent - brilliant, incisive in debate, of incredible skill and persuasive power," he said.
Mr Blair said Mr Cook had been a "close colleague". "He was always stimulating, energetic and, of course, grasped every detail of his brief.
"Though we disagreed over Iraq, I always respected the way in which he put his case."
Gordon Brown called him "one of the greatest parliamentarians of our time", praising his "forensic skills" and "formidable debating prowess". "All of us recognised that his disagreements over Iraq arose from principle," said the Chancellor of Mr Cook, to whom he had lately become close after decades of rivalry.
For the Conservatives, Michael Howard said: "Robin Cook's contribution to British politics was immense. He was a politician of principle who fought hard for the things he believed in. He will be greatly missed."
The Liberal Democrat leader, Charles Kennedy, said: "Scottish, British and international politics have lost a good and gifted man. Robin was a genuine radical and reformer by intellect and instinct - with a personal zest which matched his deep political integrity. As such he gave the business of politics a good name."
It was left to former colleagues, however, to give a more complete appreciation of a man who, for all his wit, sometimes cut a lonely figure in Westminster.
John Williams, the Foreign Office's director of communications, said: "Of course his intellect was formidable, but he was vulnerable, a very real human being. The criticisms of him hurt, and he really wanted to be a foreign secretary who made a difference."