Former long-distance runner Steve Cram believes that concern will surround this Sunday's London Marathon following the blasts in Boston.
This weekend's event is due to go ahead, despite two explosions killing at least three people and leaving over 100 injured near the finish line of the Boston Marathon yesterday.
Security measures are due to be reviewed ahead of the marathon, but former Olympic athlete Cram trusts that runners and spectators will be safe.
"I think people will be concerned, people who would either be coming to spectate or take part, but I know the team at London very, very well and London is renowned as being one of the best organised events in the world," Cram told BBC Radio Five Live.
"We have a fantastic record in the UK of doing everything to stop this sort of thing happening, but there is only so much you can do. Boston is the oldest established marathon in the world.
"It has a great tradition and that's why people want to go and take part. These events attract people from all parts of society and all parts of the world and that's the shame of it, because it's not an attack on America, but on all of us."