Post-13 Who am I?

It came as a suprise to me that Poirot had ecussed Sheppard, such a nice man he apeared to be. Poirot kept him by his side the whole time, never did i suspect him at all. I don't know how it slipped my hands all the clues were there nowhere to hide nowhere to run. If only i had the knowledge he does i would be twice as big as i am now. However i thank him for his work, I should head back to my office the only place in this town with peace. It should be a while before another event like this occurs, at which time i hope Poirot will come again to my assistance.