That three of the London bombers should have come from Leeds, and that one should have worked in schools, spread disbelief and anxiety throughout the city.
But, when the shock of the events of July 7 died down, it created a determination that children would grow up proud of this culturally diverse city.
A year on, and schools are working doubly hard to improve community cohesion.
Lesley Dolben, head of Harehills primary, where 92 per cent of the 528 pupils speak English as an additional language, said: "I saw the Muslim community close down. More very young children wore headscarves"
Hanif Malik, a project leader at the Hamara Healthy Living Centre, where bomber Mohammed Siddique Khan was an outreach youth worker, said the bombings had made the Muslim community look in on itself.
He said: "We questioned whether we were still part of British society.
There was no use in papering over the cracks. We had to change stereotypes."
The need to bring communities together was spearheaded by two of the city's Muslim leaders. Jamil Ahmed, general secretary of Leeds Islamic Centre, and Solat Chaudrhi, formerly chief executive of Learning Partnerships, were so concerned that Leeds' diversity should be recognised as an asset that they gave up their jobs to set up the National Centre for Diversity, and alongside it, Investors in Diversity, a national standards organisation, like Investors in People, launched last week.
Mr Ahmed said: "After 77 we had two options. We could have buried our heads in the sand or risk our livelihoods to try and bring about change. We opted for the latter."
Ms Dolben believes schemes such as Investors in Diversity will transform her school. She said: "I've already introduced flexible working, taken on parental support assistants, learning and academic mentors, and inclusion managers.
"In 2004, I had seven applications for a teaching post. This year I had 195 applications for five posts because we are seen as a diverse and excellent institution. But we want to be better."