Cox was born in 1939 at Oxford, England. He was in the British Merchant Navy, and was a chief officer with the Union Steam Ship Company before becoming a chartered accountant in Palmerston North.[1]
He represented the Manawatu electorate in Parliament from 1978[2] to 1987, when he was defeated by David Robinson. From 1981 to 1985 he was Junior Whip for the party.[1] He was an opponent of National's then leader Robert Muldoon and was an organiser in the Colonels' Coup, an abortive attempt to remove him from the leadership of the party.[3]
In 1984 Cox was appointed Shadow Minister of Revenue by Muldoon.[4] In 1985 he was additionally given the Customs portfolio by new leader Jim McLay.[5] Cox was a key supporter of McLay and became his "numbers man" in the caucus.[3] In a major reshuffle in February 1986 McLay promoted Cox to the position of Shadow Minister of Finance.[6] His elevation to the high profile finance portfolio role did not last long and after McLay was deposed by Jim Bolger he was relegated to the Customs portfolio once again and was additionally made Shadow Minister for the Audit Department.[7]
In 1989 he sought the National Party nomination to stand in the Auckland seat of North Shore at the 1990 election, to replace the retiring George Gair. He was narrowly beaten in a members ballot by Bruce Cliffe.[8]