Why was Booth admitted into the presidential box?

[RJNorton]

John, I am currently reading both your book and Betty's second edition. Most certainly I am enjoying both. I commend both of you!

John, I am curious about the statement Clara Harris gave which was published in the New York Herald. Here's a part:

"Nearly one hour before the commission of the deed, the assassin came to the door of the box and looked in, to take a survey of the position of its occupants. It was supposed at the time that it was either a mistake or the exercise of impertinent curiosity. The circumstance attracted no particular attention at the time. Upon his entering the box again, Maj. Rathbone rose and asked the intruder his business. He rushed past the major without making a reply, and, placing his pistol close to the back of the president’s head, actually in contact with it, fired, and instantly sprang upon the cushioned baluster of the box, when he made a backward plunge with his knife, aimed at the face or breast of Mr. Lincoln. Maj. Rathbone, springing forward to protect the president, received a stab in his arm."

As far as I know there is no other eyewitness evidence that John Wilkes Booth made a "trial run" about an hour before the assassination. Don't you find it strange that Clara was apparently the only one to see this? Also, she states, "Upon his entering the box again, Maj. Rathbone rose and asked the intruder his business." As far as I can tell this is in direct conflict with what Rathbone said - that he was intently watching the play (with his back to the door) and was not aware of Booth's presence in the box until the shot was fired.

Although Brooks does write about the Harris' account on p. 189 he also says, "Miss Harris, hearing the door open a second time, looked up and saw Booth enter deliberately but rapidly, walk up behind the President, whose face was turned toward the audience, and applying a little pistol exactly under the left ear, fire." I assume this information also comes from the Clara Harris' account?

How much veracity do you place in Harris' account? I ask because the implication seems to be that both Henry and Clara were fully aware that Booth had entered the box. This whole concept is new to me as I was of the opinion that both Clara and Henry were intently watching the play and both were not aware of anything amiss until the actual sound of the gun.