Reports emerged late last month that Sharp helped facilitate the loan just prior to his appointment as BBC Chair.
Blyth is acting as guarantor of the loan.
Sharp reported this soon afterwards to UK Cabinet Secretary Simon Case, he said on several occasions today.

Richard Sharp (left) and Boris JohnsonHouse of Commons/PA Images via Getty Images
This is an ambiguous construction, said Sharp of the memo.
I have never given Mr Johnson financial advice.
I know nothing about his [financial] affairs.

This was to protect my position and protect his.
Blyth refers to Johnson by his old family nickname Al, Sharp said, while Sharp calls him Boris.
The brouhaha was taking place in the summer of 2020 and Sharp was appointed BBC Chair shortly afterwards.