CHRIS Patten makes a good speech. He knows when to expand at length on the need for others to take responsibility for their actions. He also knows when to skirt round the points which reflect badly on him. Speaking at the inauguration yesterday of the Freedom Forum Asian Centre, he was very sound on the principle of freedom of expression. He was forthright about the need for journalists to guard against the ''insidious enemy'' of self-censorship. And he was encouraging, but all too brief on the present progress in reviewing and amending current legislation on telecommunications and broadcasting to safeguard freedom of expression. A great deal more detail would have been welcome. It is nonetheless gratifyingthat the Government has taken the Journalists' Association's fears on board. Mr Patten should be congratulated for taking action where previous administrations have preferred to retain their instruments of media control. But on freedom of information he was disappointing. Even when asked directly if he would favour a Freedom of Information Act, enshrining the principle of free access for all to government information, he would only say he had reservations on it. He did not elaborate on those reservations, but he should abandon them now. That caution is a hangover from his days in Britain, where politicians have traditionally called for freedom of information in opposition and then found it expedient to retain controls in power. Secrecy encourages abuse of power and undermines the credibility of the media Mr Patten claims to support by making informed debate impossible. Democratic governments which have opened their files to public scrutiny have not been rendered impotent as a result. Nor have they found the operation of truly open government excessively expensive or time-consuming. In Hong Kong, where secrecy has been the hallmark of colonialist administration in the past and threatens to aid repression in the future, it is a legacy of British rule which should be eliminated before 1997.