Peace campaigner Mike Haines has said he has wrestled with feelings of hatred every day since the brutal murder of his brother.
Aid worker David Haines, from Perth, was captured and killed by Islamic State terrorists in an act of terror which sent shockwaves around the world.
His brother has spent the last three years speaking to more than 10,000 people and religious leaders, as part of his Global Acts of Unity campaign.
Mr Haines was talking to students at a school in London on Wednesday morning, just hours before Khalid Masood drove his car at pedestrians on Westminster Bridge.
The 50-year-old, from Dundee, has called for unity in the wake of the attack.
But he admits that he faces a “daily battle” with hate.
Mike told Sky News: “At the moment, feelings are very raw, there’s a lot of nervousness and fear. One of the things that we have to do is accept this. It is only natural to have these feelings.
“But it is very important that we stand together.”
He said: “The past few days, here in London, one of the things I have seen is that Blitz mentality. We have been under attack, but we are going to stand united against it.
“It has been multi-faith and multi-cultural and it is almost like the silver lining to the cloud when something bad has happened.
“No matter who perpetrates the atrocity, it is the reaction we have to it. We can either take that path down to hatred and division and let people divide us, bring fear and discord into our society. Or we can stand shoulder to shoulder and let our voices be known.
“Now the time has come to unite our voices against the voices of hatred and drown them out.”
Mr Haines added: “I must admit I have this daily battle with hatred. I could easily slip down that path.
“I have been visiting schools throughout our great country and beyond and I have been met with nothing but warmth, compassion, care and friendship.
“The response has been wonderful.
“I can’t do anything to bring my brother back, I wish I could. So I try to stand by those values that my mother and father gave to David and I when we were kids: A belief in multiculturalism and multifaith.
“No matter who we are, we all have our right to our own beliefs, our own society and of course our heritages.”