The international diplomatic effort to push Syria's warring parties to the negotiating table continues - as does the mission to eliminate the Assad's regime stockpile of chemical weapons. But all the while the suffering of Syrian civilians intensifies. HARDtalk speaks to David Nott, a British surgeon recently returned from 5 weeks practising frontline medecine in rebel held Syrian territory. He calls it the most troubling experience in his 20 years of crisis care. In a conflict such as Syria's how much difference can a courageous doctor make?