His resignation from the Cabinet in opposition to the war in Iraq in 2003 was a mark of the man. He was a committed socialist of the old-fashioned kind - despite paying lip-service to "New'' Labour orthodoxy - and he did more by that act to demonstrate the importance of principle over pragmatics in politics than any of the self-justifying speeches of his more easily manipulated colleagues over the war.
Cook had been delighted to be made Foreign Secretary when Tony Blair took office in 1997, although his early monthswere blighted by the scandal caused by his love life. His years in the job may not have led to any significant changes in foreign policy - his declaration of an "ethical'' policy was a sort of repeated mockery - but he was capable and competent.
It was a disappointment to him to be moved after the 2001 election, and it was also clearly easier for him to resign subsequently and give a political lead to those opposing United States adventures in Iraq. It is possible that Mr Cook still believed the New Labour experiment might crash, and that in such an event it would be Mr Cook who had the clean hands to take up the reins.
It was as a political operator that he was less skilful. He rose so swiftly through the Scottish political ranks that he developed a somewhat arrogant manner. This excessive self-confidence, coupled with a degree of vanity, created a distance between him and his colleagues that could cause offence. His pursuit of his career made him enemies in the party, and he had a tendency to pomposity that did not serve him well in office.
Despite this, most of his colleagues were prepared to forgive him most of the time. They had to because he was so often right. The problem for him, however, was that it did not put him on anyone's list as a popular choice for party leader. He was desperately hurt by that and deeply resented the idea that his looks might also hamper his career.
It was his socialism which propelled him into politics. Like any other Labour politician who had lived through the miserable years of internal warfare in the party that followed the 1979 general election defeat, Cook recognised the need for internal reform. He was never an enthusiast for New Labour and all its works. He was too Scottish for that. But Cook was able to compromise. For, like all his comrades, he was very anxious for office.
One of the mysteries of his political career was a lifelong dispute with the Chancellor of the Exchequer, Gordon Brown. The reason why the two disliked each other has never been clear. The most likely suggestion is that it was caused by a row at the publication of a book which they jointly edited. Mr Cook was late and Mr Brown began the meeting without him. What is more fundamentally true is that the two men recognised in each other an equivalent intellectual ability and a matching ambition.
Julia Langdon's books include a biography of Mo MowlamReuse content