The loss of Robin Cook is devastating for his wife, Gaynor, his family and his friends. But it is also devastating for the Labour Party, its present and its future. Devastating to those countless party members who were inspired by his oratory and his ability to give living passion and energy to socialist values. When he was in the cabinet, people knew they had someone right at the top who could speak and act for Labour's soul.
Labour's left has regularly thrown up figures who could rouse a Tribune rally and warm the hearts of the faithful, but they were never credible, leading figures of government able to deliver on difficult issues and appeal to a wider audience. Robin could both rouse and govern.
Not that he was by any means the left's darling. When he was foreign secretary defending sanctions against Saddam Hussein's Iraq, or weapons sales to Israel, he provoked vitriol.
There was nobody like him in any party, of his generation, who could so command the House of Commons. His virtuoso speech on the Scott report, attacking the Tories over their illegal sales of arms to Iraq, was the finest parliamentary performance any of us present could remember. It still is. Maybe it always will be.
The night before he gave it, he asked me to his Commons office to rehearse that speech. It was electrifying. Next day, when he was ushered, Orwellian-style, into a locked Whitehall room to read the Scott report a couple of hours before he was due to speak on it, such was his formidable grasp of the whole picture that he merely needed to slot in the odd paragraph reference. The speech, which destroyed John Major's government, hardly needed a comma changed.
Robin's intellect was awesome. As his deputy in the Foreign Office, I saw him grasp a complex brief and transform it in minutes into powerful negotiating strategy, which he could communicate in the most straightforward terms. He could pick up any problem, issue or opportunity and turn it into a policy with real politics underpinned by Labour's values. Where others in government could sound technocratic, Robin was always political.
While he was tribally Labour, he was also non-sectarian, working with others both inside and outside the party to win support for policies he believed in, particularly constitutional reform and the modernisation of parliament. He may not have been televisual - as he used ruefully to concede to his friends - but he could win over any audience, from Tory-inclined businessmen to left-wing trade unionists. Articulate, witty and incisive, he could command any broadcast or meeting.
He was also courageously far-sighted. He rang me in the middle of the 1983 election campaign to ask whether I would back Neil Kinnock for leader and I was very happy to do so. During the early and mid-1980s, when the Labour Co-ordinating Committee - often unsung for its central role in making Labour credible again - had to confront from the party's left both the destructive fundamentalism of Militant and those on the party's hard left comfortable with the party's narrow base, Robin was the star on our platforms and the source of sound ideological advice. More recently, as leader of the Commons, he was determined to bridge the worryingly large gap between politicians and citizens, with the government tied more closely in to parliament. But this brilliance - which many of his jealous rivals and colleagues associated with prickliness or aloofness - was just one part of Robin the leading Labour figure.
The other part was a radical commitment to democratic reform, to environmentalism, to human rights, to equality and to social justice - those Labour values that are so crucial to Labour's future, a future badly diminished without him.
For Labour to win a fourth term and continue transforming Britain in a way that will block That-cherite extremism from gaining its malign grip ever again, we must not forget Robin's political agenda. Such as democratic reform of the House of Lords. Green energy. Narrowing the gap between rich and poor. Europeanism. Conquering world poverty and promoting justice worldwide. These were close to Robin's heart and must remain close to Labour's in future.
But it would be quite wrong to interpret this as a call for the return of "old Labour". If Robin was not really "new Labour" (I never heard him self-appropriate that label), he was certainly not "old Labour" either. His was a radical, modernising, reforming vision laced with steely practicality and a willingness to take the tough decisions. He acknowledged both Tony Blair's extraordinary appeal to Middle Britain and Gordon Brown's extraordinary economic management as giving Labour a governing credibility and a hat-trick of victories we had never before achieved in 100 years of party history. Their leadership has delivered a salutary lesson on how Labour can and should govern, with economic competence a watchword and the centre ground never neglected.
Yet Robin wanted much more. He believed Labour could build on the success of winning a historic third term by projecting a renewed radical vision. Although he resigned over Iraq, he did so without bitterness and remained on good terms with Tony Blair. He spent much of this year's general election tramping around marginal seats, pleading with those who were against the Iraq war to stay with Labour. Some Labour MPs might owe their narrow victories to him. Certainly many disheartened supporters felt better for hearing him.
The progressive voters whom Labour lost at the May election - and who cost us a lot of seats to the Conservatives by abstaining or voting Liberal - have to be won back if Labour is to beat the Tories again. Many of those voters identify with Robin's principles and his policies. They will wonder just where the party is without him.
If he is not to be as sorely missed in the future as we all feel he is today, those voters will need to feel that Robin's political legacy is not being forgotten by the Labour government in which he played such a crucial role.
Peter Hain is Secretary of State for Northern Ireland and Secretary of State for Wales