The former head of Pik Uk prison, accused of taking a $1.5 million bribe from a prisoner, went free yesterday after the case against him collapsed. Leung Kwai-hoi was charged with accepting a bribe from Wong Chai-chung to secure his early release. It was alleged he needed the money to buy a karaoke and mahjong business. Released with Mr Leung, 48, were Mr Wong, 43, Hui Wai-kwan, 33, and Leung Oi-wah, 28, Mr Wong's girlfriend. All four denied charges of conspiracy to offer an advantage. Mr Leung also denied the charge of accepting an advantage. 'Since the witnesses had given conflicting evidence the prosecution believed they could no longer be relied upon and declared them hostile,' prosecutor Peter Callaghan told Judge Carlye Chu Fun-ling in the District Court. He said the prosecution would offer no evidence as 'there was no realistic prospect of a conviction'.