The information requested can be provided through the examination of individual case files only at disproportionate cost. The chief executive of the UK Border Agency advised in her letters of 20 November and 17 December 2007 to the Home Affairs Committee that there were 1,500 foreign national prisoners detained upon completion of their sentence. She also advised during her appearance before the Committee on 15 January this year that a significant number of foreign national prisoners come from Jamaica, Nigeria, China and Vietnam.