Can a handshake transform a region?   After long years of tension, Saudi Arabia and Iran decided in March to normalise diplomatic relations. Weeks later, the Saudi and Iranian foreign ministers met face-to-face - and the handshake took place.   The landmark agreement entails patching up the rift by reviving a security cooperation pact, reopening embassies within two months and resuming trade, investment and cultural accords. The China-brokered deal could lead to a major realignment in the Middle East. And, while it is a coup for Beijing, it represents a geopolitical challenge for the United States.   This week on Beyond the Headlines, host Ismaeel Naar looks at how Saudi Arabia and Iran were able to finally reach the negotiating table - and asks what the thawing of ties means for the wider region.