Gene Hunt had heard that young Bones was going to investigate Bletchley, and decided to invite himself along for the interview. It wasn't that he didn't trust the girl - she was very thorough.
It was the fact that Bletchley had a history as being a bit of a loose canon with a violent streak - Hunt had read the report. He was taller, and meaner looking than Bletchley, and well, Bones was only a slip of a girl, who could no doubt hold her on in a fight. But Gene would much rather prevent her from getting into such a situation.
Bletchley looked flustered when he answered the door. Gene folded his arms, and stood there, glaring as Bones showed just how polite she could be.