Hill was awarded the Centenary Medal for "service as Minister for Defence". In July 2005 the Coalition parties took control of the Senate and Hill became the first Government Leader in the Senate since 1981 to command a majority in the chamber. In January 2006, Hill announced his resignation from the Ministry and as Leader of the Government in the Senate. He did not specify a reason for his resignation, but said it was his decision to retire and he had not been pushed into it by the Prime Minister. However, one of The Age's senior journalists, Michelle Grattan, said on 31 March 2008 "Hill had not really wanted to leave Parliament, but John Howard was anxious to get him out." On 15 March 2006, Hill resigned from the Senate and, two days later, was appointed Permanent Representative to the United Nations for Australia, replacing Caroline Millar. He served in that position until May 2009. The diplomatic appointment made upon his retirement from Parliament was arranged by Foreign Minister and former Liberal leader Alexander Downer. Hill and Downer were factional rivals in their home state of South Australia and Downer was keen to see Hill out of Parliament as part of Downer's long-term plan to return to the Liberal Party leadership which never eventuated. It has been alleged that when Downer was Opposition Leader in 1994 he had failed to back Hill's bid to move to the Lower House for the seat of Boothby. Hill's diplomatic appointment had been criticized by then Shadow Foreign Minister and future Prime Minister Kevin Rudd who had doubts about Hill's diplomatic skills and said that the Howard Government had used the diplomatic service as "a Liberal Party employment agency" and this had left diplomats without the capacity to realise their ambitions. Prior to Hill's retirement in 2006 he voted for legalizing the abortion drug RU486 which had been banned in Australia up until that point As Liberal Government Senate leader Hill had expressed the importance of the transition of the Prime Ministership from Howard to his Liberal deputy and heir apparent Peter Costello be smooth. It was a transition that never eventuated when Howard lost government at the 2007 election and Costello refused to succeed Howard as Liberal leader. Later career Following his return to Australia in 2009, Hill accepted an appointment as Adjunct Professor in Sustainability at the US Studies Centre at the