Who leaked the Hutton report?

"In the interests of fairness I gave advance copies of my report to the parties 24 hours in advance of publication subject to strict undertakings as to confidentiality, and it is all the more regrettable that the newspaper [The Sun] published its report of some of my conclusions when the public had only to wait for half a day before I published the full contents of my report.

I am now giving urgent consideration to what investigative and legal action I should take in respect of the newspaper and its source."