He is mentioned here, Evidence submitted to the Inquiry by Thames Valley Police, by way of a witness statement labelled thus:
Witness statement: Alan Clark - not for release - personal witness statement TVP/1/0046 - 0047
Alan Clark wasn't a witness at the Hutton Inquiry, yet he clearly had some interesting information potentially to impart.
For example, in this document, TVP_3_0002, we learn that Mr. Clark had provided seven exhibits six of which were labelled as "sensitive".
I intepret the preceding page as being part of the following document from Kevin McGuire:
Covering note from Kevin McGuire 08/08/03 - not for release - Police operational information TVP/3/0001 - 0003
One might also ask "Who is Keven McGuire?".
In 2010 it would seem that Kevin McGuire was/is a Detective Inspector with Thames Valley Police: Men sentenced to over 10 years imprisonment for game machine theft - AMENDED.