Educated at Glasgow University, he spent some time at the University of Arizona and worked for Shell Oil in California.
He was chief executive of the Inner London Education Authority, then head of the Further Education and Funding Council, one of the country's largest quangos, from 1992 to 1996. He joined the Qualifications and Curriculum Authority when it was established in 1997.
When David Hargreaves, its former chief executive, announced he was leaving after less than a year at the helm, Sir William was forced to take up a more hands-on role at the quango.
The 64-year-old, who was knighted in 1994, has a reputation for "calling a spade a spade" which has made him unpopular in some quarters. It was Sir William who demanded extra powers from the Government to intervene in exam boards.
He told the Commons select committee earlier this year that he and his board would resign if there was any political interference with exam standards.
In June, Sir William clashed publicly with Education Secretary Estelle Morris when the minister made it clear that the watchdog carried the can for recent problems with the exam system, including exam paper blunders.
KEN BOSTON, the new Australian head of the QCA, has had a baptism of fire. He has staunchly defended the quango's innocence in the A-level fixing debacle. In doing so, he has alienated hundreds of teachers by blaming poor module results on their lack of understanding of the demands of the new A2.
His report, published last Friday, which looked only at those students who had received A, A, U grade profiles, was described as a whitewash.
Mr Boston is no stranger to teachers' displeasure. The 59-year-old was director general of education and training in New South Wales, the largest school district in Australia and the country's largest employer.
Three years ago, he accused teachers of being greedy during a pay dispute They immediately went on strike and called for his resignation.
The pound;120,000 chief executive's impressive record in vocational education is his biggest selling point as the quango attempts to formulate government plans to overhaul secondary education.
RON MCLONE, OCR chief executive, has worked in the complex world of public exams for nearly 20 years. The mathematician has been described as a survivor and a stickler for detail. Given his reputation for caution, other exam experts are astounded that grade profiles where whole classes received five As and a U were ever released.
Dr McLone is a former academic who joined the University of Cambridge Local Examinations Syndicate in 1985. When the Oxford, Cambridge and RSA boards merged, he survived and rose to the the top of OCR when many other senior figures fell by the wayside.
He is a fellow of the Royal Society of Arts, the Institute of Mathematics and the Royal Meteorological Society.
OCR faced a storm during last year's GCSE results when former examiner Jeffrey Robinson claimed GCSEs papers were easier than they used to be.