Hagay Shefi always was early for things. In his 20s he already headed a unit in Israel's Defence Ministry's budget department. A brilliant officer, he had been seconded from the IDF's elite Centre of Computing and Information Systems.

By his early 30s he was heading up cutting-edge high-tech companies in the international financial sector and, on the morning of September 11, not yet 35, he arrived early at the conference centre on the 106th floor of the World Trade Centre's North Tower, to prepare a lecture to a group of New York bank managers.

Twenty minutes after the first passenger plane struck the tower, it was already clear that there was no way out and he called his wife Sigal to say farewell. At five minutes past nine, the call was cut off.

"I admired him in a way I can't explain," says his father, Dov Shefi, who participated on Sunday in the memorial services in New York, a decade after the 11/9 terror attacks.

"He succeeded in everything he did, he was a perfectionist."

Dov and his wife, Esther, saw Hagay for the last time five months before the attack. "We flew to New Jersey to spend Pesach with them. Hagay insisted on conducting the Seder himself. He did it perfectly, like everything else."

Dov is very careful with his words, as befits a legal expert and military man. A former IDF brigadier-general, he served as the military attorney-general, the defence ministry's chief legal counsel and a special adviser at Israel's embassy in Washington. When he describes the World Trade Centre attack as "one of the biggest war crimes in history", he does so in strictly legal terms. "They attacked what was a clear civilian target, in the knowledge that there would be many thousands of civilians there, breaking the fundamental principle of distinguishing between combatants and non-combatants. The same principle does not apply, for example, to the attack on the Pentagon the same day."

Two years before the attack, he visited New Jersey with Hagay, where he gave a lecture to a faculty of the American military academy West Point.

"I spoke to them about the first attempt to topple the World Trade Centre with an explosives truck in 1993," he recalls with a faint smile of irony.

"I told them that was nothing compared with what would happen if the US did not prepare itself for future attacks. I said they had to realise that they couldn't cling to the constitutional rights of enemy civilians at the expense of the safety of their own civilians.

"When I visited the US again after the attack, and we were thoroughly searched at the airport, I was happy. I felt Hagay's death hadn't been in vain. They wouldn't allow 19 terrorists with knives on a plane ever again."