British police investigating the involvement of the country's foreign intelligence service in the secret abduction of Libyan suspects, including one taken from Hong Kong, and their forced return to Tripoli have handed over a file of evidence to the Crown Prosecution Service. The latest development in the inquiry comes the day after Abdul Hakim Belhaj, one of the men who was returned to Muammar Gaddafi's intelligence services, won the right to sue the British government in court over his treatment. The Metropolitan police investigation, codenamed Operation Lydd, into the rendition of Libyan opposition activists in 2004 is considering the role of British officials in the combined operation by MI6 and the CIA. Belhaj and another dissident, Sami al-Saadi, spent six years in jail and were, they say, frequently tortured. In March 2004, Saadi - along with his wife and four young children - was forced onto a flight out of Chek Lap Kok to Tripoli. CIA documents detail the Hong Kong government's complicity with British and US spies involved in the rendition. A Metropolitan police spokesman said: "The submission of the file is part of the ongoing investigative process and should not be taken to indicate that the police investigation is yet concluded." Britain's central role in the renditions emerged after the fall of Tripoli in the 2011 revolution when correspondence from a senior MI6 officer, Mark Allen, was found in the office of Gaddafi's spy chief Moussa Koussa. Cori Crider, a director of the legal charity Reprieve and member of the legal team for the Saadi and Belhaj families, said: "This is a welcome sign that Met investigators are treating the abuse of pregnant women and children by the state with the seriousness it deserves." Whitehall officials insist the rendition of Belhaj, Saadi, and their families to Tripoli was done at the behest of ministers. MI6 was following "ministerially authorised government policy", they insist. Jack Straw, foreign secretary at the time, has said he will say nothing about the affair until the police investigation is over. In December 2012, the British government paid Saadi more than £2 million (HK$26.5 million) in compensation, without admitting any liability. Negotiations between the Hong Kong government and Saadi are at a standstill, more than two years after lawyers first alerted justice officials to the case.