How do you stop terrorists getting their hands on the nuclear material?

President Obama and more than 50 world leaders convened in Washington in an attempt to reach global cooperation on securing nuclear weapons materials.

Dr Beyza Unal, Nuclear Weapons Policy Fellow at Chatham House said to our presenter Nick Robinson:

"I don't think there's a country that would be vowing to give its nuclear weapons or nuclear materials to a terrorist".

She said:"Security and safety of nuclear material its not there, and its not been there for many years, and that's the agenda of the nuclear security summit".

(Image: world leaders meet during the afternoon plenary session of the Nuclear Security Summit Copyright:AP Photo/Alex Brandon)