McNicol was a member of an Australian delegation responsible for negotiating the Manila Treaty in September 1954.[3] In December 1954, McNicol's appointment as Minister to Vietnam, Laos and Cambodia was announced.[4] In January 1955 the Australian Government announced McNicol's residence for the post would be at the new Australian Legation in Cambodia, to be opened in February that year.[5][6]
From 1957 to 1960 McNicol was High Commissioner to Singapore, at the time Lee Kuan Yew was moving the country towards independence.[1]
He was High Commissioner to Pakistan from 1962 to 1965[7] His Pakistan appointment was announced by then Minister for External Affairs Garfield Barwick in July 1962.[8]
In June 1968 then Minister for External Affairs Paul Hasluck announced McNicol's appointment as Ambassador to Thailand.[9] At the same time, he was also appointed Australia's council representative to Southeast Asia Treaty Organisation (SEATO).[10]
In December 1972, then Prime Minister Gough Whitlam appointed McNicol Deputy High Commissioner in London.[11]