Customs inspector Simon Hui Sai-man has spoken of his 'indescribable happiness' after donating part of his liver to save the life of a critically injured colleague. Hui wept yesterday as he spoke publicly for the first time since the operation four days ago in which part of his organ was implanted in fellow officer Yuen Wai-cheung, who had been injured in the line of duty. 'It is an amazing feeling when you see a person's life continue because of you,' he said. 'The happiness is indescribable.' Hui, whose swift recovery after such a serious operation has astonished doctors, said he had been to see Yuen - whom he had not met before the surgery - and had agreed to meet later for a game of chess. 'We had a simple conversation; Yuen thanked me and I cried as it was a touching moment,' he said. Meanwhile, doctors said Yuen, who was in a coma before the operation, was still disorientated and had trouble believing he was alive. 'Sometimes he thinks he is already dead and in hell and calls me or other medical staff Emperor of the Underworld,' Professor Lo Chung-mau, head of the University of Hong Kong's liver transplant team, said. This was normal in people who had suffered such trauma and could last for days to two weeks. 'We keep talking with him and repeatedly reminding him that he is alive in a hospital in Hong Kong,' Lo said. Commissioner of Customs Richard Yuen Ming-fai, who met Yuen and Hui yesterday, said Yuen could remember a lot of things, such as the fact he was a customs officer and had been invited to participate in the customs chess competition in January. 'I wished him to get well soon and to practise his chess skills during his recovery,' the commissioner said. Hui said Yuen, whose liver was damaged when he fell against a fence while chasing a suspected cigarette smuggler, told him he wanted to recover as soon as possible. 'I told him to be patient,' Hui said. 'We made a deal for a coming chess game.' Commissioner Yuen said doctors had been astonished by the speed of Hui's recovery. 'He opened his eyes the first day after the operation, got out of bed by himself on the second day, walked around on the third day, and asked to be discharged on the fourth day,' the commissioner said. Hui attributed his recovery to his healthy lifestyle. He is a vegetarian who exercises regularly and does not drink nor smoke. Lo has said he could be discharged as early as today. 'I really hope the public will understand the importance of their health and spend more time with their loved ones,' Hui said. Hui, who made a split-second decision to make the donation after hearing an appeal, called for more people to donate organs after their death. 'I hope my experience can deliver a positive message that we can help many people around us.'