'Cash-for-honours' timeline.

(From Guardian Unlimited)

March 2006: Metropolitan police begin inquiry.

April 13: Des Smith, a headteacher, is the first person arrested. Mr Smith, who until January was an adviser to the body that finds wealthy sponsors for the government's city academies, had allegedly suggested that backers of a flagship Labour schools policy could expect to be rewarded with honours. His lawyers later say he "categorically denies" the allegations.

July 12: Labour's chief fundraiser, Lord Levy, is arrested for the first time. He is later re-interviewed and re-bailed without charge and insists he is innocent.

July 13: The Commons Public Administration Committee calls for tighter checks on the propriety of all higher honours awards.

July 14: It emerges that police officers have already questioned at least two government ministers. The former Labour party chairman, Ian McCartney, now a junior trade and industry minister, and the science minister, Lord Sainsbury (who has since stepped down), are among 48 people …