The Metropolitan Police's Assistant Commissioner Cressida Dick, who is responsible for counter-terrorism, said her thoughts are with Fusilier Lee Rigby's family after his killers were found guilty of murder.
She told ITV News UK Editor Lucy Manning it was "an appalling act” on a “completely innocent young man with no chance to defend himself in broad daylight on a busy London street.”
When asked if a similar attack could happen again, she said: "It's our job to do everything we can to try to stop such attacks and we do have, I think, a very good record in this country.”
However Ms Dick said: "We cannot reduce the risk of something like this happening to absolute zero. We'll do everything in our power to do so."