Cook was born in Dunedin, New Zealand, in 1949 and was educated at Bayfield High School, Dunedin and the University of Otago where he did a BA (Hons) in Maths and Stats.
[3] He served as one of three vice-presidents of the International Statistical Institute from 2005 to 2007 and is a visiting fellow of Nuffield College, Oxford.
He was a member of the secretariat of the Prime Minister's Task Force on Tax Reform in 1981/82 and a member of the Royal Commission on Social Policy in New Zealand in 1987/88.
[4] He led the creation and publication of the National Statistics Code of Practice.
Probably his most publicised act in his time in the United Kingdom came in February 2005, when as Registrar General he had to rule on the legality of the wedding of Charles, Prince of Wales and Camilla Parker Bowles.