The International diplomatic effort to push Syria's warring parties to the negotiating table continues - as does the mission to eliminate the Assad regime's 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 five weeks practising frontline medicine 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?