As I watched Tony hand back the phone, I saw him slump into his seat. From sitting upright he just crashed. David Kelly was dead, he said. His body had been found in woodland close to his home. It was awful. He decided there and then that there had to be an investigation and spoke to Charlie Falconer, now Lord Chancellor, from the plane to see which judge might be available. I have never seen Tony so distraught and I felt helpless to do anything. Eventually he spoke to Alastair - God knows what time it was for either of them - who had just arrived back in London. Alastair said he couldn't handle any more and wanted out.

After a night in Tokyo in which he barely slept, Tony had a meeting with the Prime Minister while I visited a centre for disadvantaged children. It should have been a great trip. We realised soon enough that it was going to be quite the opposite. In the 25 years I had known Tony, I had never seen him so badly affected by anything. At the Tokyo press conference, a journalist from the The Mail on Sunday shouted at my husband: “What's it like, Mr Blair, to have blood on your hands?”

Throughout the trip Tony did his best to look cheerful for the sake of his hosts, but it was desperate. In Beijing we saw an installation of hand-sized terracotta figures by Antony Gormley. There is a photograph of the two of us taken that morning that I keep in my study: Tony crouching down among these thousands of tiny figures, me behind him, my arms around him, giving him the support he needed.

“You are a good man,” I told him as we crouched there, the cameras whirring. “And God knows your motives are pure, even if the consequences are not as you had hoped.” And it's true. Tony knew that David Kelly was a loyal public servant driven to despair because of all the furore, caught up in something he could never have imagined.

As a postscript to David Kelly's tragic death, his widow and grown-up children came to visit us at Chequers. We wanted to say personally how very sorry we were about what had happened. It was clear to me that what had made Mrs Kelly's life even more intolerable was the behaviour of the press after he had killed himself, to the point of taking pictures through their front windows, utterly failing to respect their privacy at all.

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