After four years of civil war Syria is all but destroyed. At least 220,000 have been killed and half of the entire population has been forced from their homes, but still the world's great powers argue over a response. Stephen Sackur talks to one of the world's wealthiest Syrians - Ayman Asfari. Asfari is an exile based in Britain and founder and boss of the Petrofac oil services corporation. Behind the scenes he has lobbied hard for a more effective international intervention in his homeland, but what would that look like?