Abbas Khan death "sickening," says David Cameron David Cameron has written to the mother of a British doctor who died in custody in Syria, describing his death as "a sickening and appalling tragedy," it was revealed last night. In a letter dated 20 December, the Prime Minister told Dr Abbas Khan's mother, Fatima, that he and his wife Samantha were "so very sorry" to hear of her son's death. "I know from my own experience of losing a child that words are of little comfort at this terrible time but please know that you are in our thoughts," he wrote. "Abbas" death is a sickening and appalling tragedy and it is right that the Syrian regime should answer for it." He branded the regime's treatment of the 32-year-old medic "despicable" and claimed it was "utterly unacceptable" that the UK were not able to support him. In a hand-written ending, he added: "You are in our thoughts and prayers." The Prime Minister's intervention came as the doctor's body was flown back to Britain yesterday to undergo a post-mortem examination to establish the exact cause of death. Dr Khan was on the verge of being released from prison when his family were last week told of his death in custody. Yesterday his relatives said he was the victim of a political murder, but the Syrian government insist the doctor took his own life. The orthopaedic surgeon, a married father-of-two from London, was captured in November 2012 in the ancient city of Aleppo just days after travelling from Turkey to help victims of hospital bombings. The International Committee of the Red Cross said it transported his body from Damascus to the Lebanese capital Beirut, where it was received by his mother Fatima Khan and British officials for the flight back to Britain. Mrs Khan, who has "110 per cent" denied claims her son committed suicide, broke down in tears when Mr Khan's coffin arrived. At the time she screamed: "The national security intelligence of Syria, they killed him! They're murderers! Yesterday the distraught mother said: "I don't know why they killed my son. I want to ask why on the release date they killed my son. I want answers why they killed my son. They are liars, every ministry there in Damascus is full of lies. They killed my son. The family took possession of his body in Lebanon on Saturday, almost a week after he was killed and intend to bury him as soon as possible after the post-mortem has been carried out at Romford Hospital. Yesterday his brother and sister, Shahnawaz and Sara Khan, said that nobody has explained to the family how he died and that they have been let down by the British authorities. In the last few days the family revealed a letter in which the doctor expressed his optimism at being released, and his hopes of being home in time for Christmas. Shahnawaz Khan said: "Everything that the Syrian government has done over these past 13 months to us has been arduous and has inflicted much insult upon us. It has been a difficult time. We haven't had a chance to grieve properly. Sara Khan said: "We want the British government to help the family in getting those answers from the Syrians as somebody needs to own up for this absolutely cruel injustice that has been done to my brother." Foreign Office minister Hugh Roberston said the Syrian authorities had "in effect murdered a British national" A post-mortem examination is due to be carried out on Mr Khan's body today.