The older brother of the leader of the London Bridge attack has apologised on behalf of his family, saying he is sorry “from the depths of his heart”.
Addressing the families of the eight people who were killed, Saad Butt said if he could turn back time he would change places with every one of them.
At the inquest into their deaths, he said his brother, Khuram, had been “the life and soul of the party”.
But he developed extreme views after becoming angry over events in Syria.
Over the last four years he had become increasingly angry, Saad Butt told the inquest, over “foreign policy, the wars, the injustices overseas”.
These “created the disgust in my brother’s heart to the place which gave my brother safety,” Mr Butt, a youth worker, said, adding: “Only God knows what he was thinking… We were from the same womb but we are different people.”
Butt, 27, and two accomplices mowed down pedestrians on London Bridge with a rented van before stabbing people in nearby Borough Market on 3 June 2017.
All three men were shot dead by police less than 10 minutes after the violence began.
Mr Butt told the inquest: “Sorry. Sorry from the depths of my heart, and on behalf of my family.
“If I could turn back time I would change places with every one of you, even if it meant losing my life to my own brother.”
The Old Bailey heard that the family had intervened in February 2015 to take away Khuram Butt’s passport and that of his wife and baby boy because they were worried he would take them to join the Islamic State group in Syria.
The attacker’s wife, Zahrah Rehman, told the inquest previously he had booked tickets to Turkey – but she had alerted her family because she was afraid he would try to take them on to Syria from there.
“He wanted to fight the armed forces on behalf of Isis,” said Saad Butt, but he said they persuaded him to drop his plans.
After that, Mr Butt said he continued monitoring his brother’s activities but never contacted counter-terror officers.
Mr Butt, who had carried out anti-extremism work with the government, said he felt “competent” supervising his brother.
There was nothing his brother was doing that indicated he should contact the authorities, he said.
“He was on their radar,” he told the inquest.
“He was reported by two family members on two different occasions in 2015.
“I’m not a Prevent [a strand of the government’s counter-terror strategy] officer. What did MI5 do about him?”
At the inquest
Keiligh Baker, BBC News
The court fell silent as Butt’s brother, Saad, sobbed as he read out a statement he had written, addressed to the families of the victims.
At several points he had to pause to audibly collect himself before continuing with the speech.
He also described a dream he had had in the April before the attack in which Butt appeared at his place of work, a youth centre, wearing a suicide belt.
Crying, he said: “He was clean shaven and his lips were blue.
“Just as he was about to detonate I hugged him. I hugged him to stop him from hurting people.
“But we cannot turn back time.”
‘Associating with extremists’
Mr Butt also told the court he did not know his brother had appeared in a Channel 4 documentary called the Jihadis Next Door in 2016 – a time when he was grieving over the death of his daughter who was killed in an accident.
When asked whether it was surprising that he had not been made aware of the programme, which showed his brother associating with extremists, he replied: “My daughter died because of third degree burns and I think, as far as the family was concerned, that was the least of my worries.
“Me and my wife totally collapsed.”
He also described a barbecue before the attack at which a friend of his brother stuck a skewer into some meat and said: “That is how you gut a Kuffar” – an unbeliever.
The event was organised by Khuram Butt to celebrate the birth of his second child, a daughter.
The inquest was shown a photo of 14 men praying outside his flat on the day.
Two of the 14 men – Butt and one of his accomplices, Rachid Redouane – would carry out the London Bridge attack three weeks later.
Breaking down into tears, Mr Butt described the early hours of the Sunday morning after the attack, when he realised what his brother had done.
“His daughter was only one month at the time,” he said. “Only God knows what he was thinking.”
Those who died were: Xavier Thomas, 45, Christine Archibald, 30, Sara Zelenak, 21, Sébastien Bélanger, 36, James McMullan, 32, Kirsty Boden, 28, Alexandre Pigeard, 26, and, Ignacio Echeverría, 39.
The inquest continues.