In the 1988 New Year Honours, Hercus was appointed a Dame Commander of the Order of St Michael and St George, for public services. She then served as Ambassador and Permanent Representative of New Zealand to the United Nations from 1988 to 1990. In 1993, Hercus was awarded the New Zealand Suffrage Centennial Medal. In 1998, she was appointed Deputy Special Representative and Chief of Mission of the United Nations operation in Cyprus; at the time of her appointment she had been working as a special advisor to the United Nations. After one year as Deputy Special Representative, she was promoted to Special Representative. In this role, she had been attempting to arrange direct negotiations between Turkish Cypriot leader Rauf Denktas and Greek Cypriot President Glafcos Clerides; however, after a month in this role she resigned for family reasons and returned to New Zealand. She subsequently served as a member of the UN Secretary General's Eminent Persons Panel on Peacekeeping Operations in 2000. Hercus has served on a wide range of NGO Boards and Boards of State Owned Enterprises. These included the New Zealand Women's Refuge Foundation 1996–98, the New Zealand Richmond Fellowship 2005–07, the Board of the Theatre Royal Charitable Foundation 2005-08 and the Residual Health Management Unit later renamed the Crown Health Financing Agency. In 2002, Hercus was appointed by the Minister of Broadcasting Marian Hobbs to the board of Television New Zealand. She resigned this position in December 2004, following her decision as a member of the Board's Remuneration Committee to decline to support the majority decision of this Committee and subsequently the Board that “they would reluctantly have to concur" with the 50% increase in salary to $800,000 offered by CEO Ian Fraser to newsreader Judy Bailey. She was persuaded to remain on the Board by the Minister. A year later on 8 December 2005, she formally resigned from the Board of TVNZ. The day this resignation was announced on 14 December 2005, was coincidentally within hours of former CEO Ian Fraser appearing before a Parliamentary Inquiry into Television New Zealand Ltd by Parliament's Finance and Expenditure Committee. Hercus was the fundraiser for 'Save our Arts Centre', an organisation opposing the development of a new building for the School of Music for the University of Canterbury at the Arts Centre. Resource consent hearings before independent Commissioners denied this resource consent and the plans lapsed. The University's School of Music and Department of Classics has moved 8 years later into the heritage Chemistry Building at the Arts Centre. Hercus now resides in Christchurch New Zealand.