One of Ireland’s top policemen has arrived in Beirut to head a UN team investigating the assassination of Lebanon’s former prime minister.Peter Fitzgerald will probe the circumstances, causes and consequences of the killing of Rafik al-Hariri. “We intend to carry out our mandate in a timely manner and then we intend to report to the Secretary General of the United Nations in order for him to fulfil his directives from the Security Council to report back within four weeks,” he said. The Lebanese opposition has blamed the bombing on Syria. It comes amid renewed international pressure on Damascus to withdraw its thousands of troops from Lebanon and to loosen its political grip on Beirut. Demonstrations against the pro-Syrian Lebanese government have become an almost daily event. Damascus has denied any involvement in Hariri’s killing, and says it is preparing to pull its army back.