User blog comment:Hitsuji Mamoru/Servant Creation Room 2 : Guess of the Who/@comment-4802891-20170313083653/@comment-4802891-20170316153907

EX rank just mean it has the side effect of "backfiring" the effect on him as a permanent buff to his overall parameters. If it wasn't for this special effect, he would have A rank.

To answer your question, he never put his trust in someone famous enough to be considered a Heroic Spirit.

As a new hint : he was a real person, but most people will refer to his fictional counterpart, more often than the real person the litterary hero is based on.