It's taken 9 years of on-off negotiations - but finally - today -- the world's major powers reached an historic deal with Iran on limiting its ability to develop a nuclear weapon. In return - the leaders agreed to lift economic sanctions against Iran that have crippled the country for 13 years. President Obama said the deal would make the world "safer and more secure" while Iran's President Hassan Rouhani said it opened a "new chapter" in Iran's relations with the world. We begin our special coverage with this report from our World Affairs correspondent Richard Galpin.
