A former Islamist radical who now works to challenge extremism has spoken of meeting the father of a teenage suicide-bomb victim in Israel.

The first time Maajid Nawaz, the co-founder of the Qulliam think tank and the author of a new memoir about his time in Hizb ut-Tahrir, went to Jerusalem, he spoke only to other Islamists.

Returning 11 years later as part of a Liberal Democrat Friends of Israel delegation that toured everywhere from Sderot to the West Bank, Mr Nawaz said the trip had left him better informed.

He said the reaction when he told Israelis and Palestinians about his past had been overwhelmingly positive. “I told a victim of terror, who lost his daughter in an attack [about my background]”, he said, referring to Arnold Roth, whose 15-year-old daughter Malki was killed in the Sbarro pizzeria bombing in August 2001.

The co-conspirator of the attack, Ahlam Tamimi, was freed last year as part of the Gilad Shalit prisoner exchange, and has since said that she has absolutely no regret for the deaths of 15 civilians.

“Mr Roth had heard of Quilliam and he actually congratulated me. He said, ‘what you’re trying to do is what is needed and I really wish you success.’”

Mr Nawaz, who was jailed in Egypt soon after his first trip to Jerusalem, said that the recent visit was the first time he had gone “to hear both narratives.

“The language that I use will be lot more precise now,” he said. “I went there with the term ‘separation wall’. We met the colonel who originally designed and built the wall, and he clarified that 95 per cent of the barrier is in fact a fence.”

He said he hoped more Muslims would be able to have this experience. “People who come are confronted with reality. I was on the beach in Tel Aviv and in front of me was a mosque.

“There were Muslim women in headscarves playing with their kids, and next to them were Orthodox Jews and they were all together.

“That’s a reality that, if visually you behold it, you are forced to stop viewing it as a ‘clash of civilisations’”.

He said that seeing Israel five years after he left Hizb ut-Tahrir was meaningful on a personal level. “There are still emotions that I need to confront — and these sorts of trips help me.”