From May's letter...
"am therefore concerned by the manner in which you have engaged with this investigation.
It has been conducted fairly, with the full co-operation of other NSC attendees.
They have all answered questions, engaged properly, provided as much information as possible to assist with the investigation, and encouraged their staff to do the same. Your conduct has not been of the same standard as others.
In our meeting this evening, I put to you the latest information from the investigation, which provides compelling evidence suggesting your responsibility for the unauthorised disclosure.
No other credible version of events to explain this leak has been identified."
So presumably he DIDN'T answer all the questions, encourage his staff to help or provide info........ he wouldn't have stiffed him unless he was being slithery as hell I guess.......