Professor Hill, who has led Royal Holloway since 2002, will step down at the end of July. He handed in his notice at a meeting of the university council on 25 March.
A university spokeswoman said: “Professor Hill will take sabbatical leave until his retirement in 2011, and during this time will pursue personal research interests, alongside representative roles and special projects or consultancies for the college.”
She added: “Over the last seven years, Royal Holloway has enjoyed considerable success and is very grateful for [Professor Hill’s] leadership during this time. Student and staff numbers have increased significantly, the budget has doubled and the college has been able to make major investments in its estate and facilities.
“The 2008 research assessment exercise ranked Royal Holloway among the UK’s most highly rated research institutions, and in particular recognised its outstanding record in world-leading research.”
Professor Hill said: “I have greatly relished the challenges of leading the college during this exciting time, but now, at the beginning of a new and important period as the merger with St George’s is developed and implemented, I believe that Royal Holloway will benefit from new leadership and direction, and the fresh perspectives and insights that this will bring.”
The university will inform the Higher Education Funding Council for England that deputy principal Rob Kemp will be the “designated officer” in charge of the institution until a replacement head is appointed.
Meanwhile, Professor Willcocks announced that she will step down from her post at the end of April 2010.
She joined York St John in 1999 and has steered the institution, which has a Church of England foundation, through its relocation to a single campus in York and the award of university status in 2006. In 2008, she received a CBE in recognition of her services to higher education.
Robin Hall, chair of governors at York St John, said: “Dianne Willcocks has successfully led York St John through very significant change over the last ten years. She has carried out that leadership role with an energy and passion that engages all those around her.
“Through her skilful management of change, she has created a distinctive forward-looking university with a focus on collaboration. At the same time, she has maintained the university’s warmth of welcome and sense of community. We are saddened by her decision to step down and wish her well in her future ambitions.”