After examining it attentively, without any hint whatever from me, he identified it as the portrait of the sick man, Graves." "Indeed!" exclaimed Marchmont.

"This is most important.

Are you prepared to swear to the identity, Dr.Jervis ?" "I have not the slightest doubt," I replied, "that the portrait is that of Mr.Graves." "Excellent!" said Marchmont, rubbing his hands gleefully; "this will be much more convincing to a jury.

Pray go on, Dr.Thorndyke." "That," said Thorndyke, "completes the first part of my investigation.
We had now reached a definite, demonstrable fact; and that fact, as you see, disposed at once of the main question--the genuineness of the will.
For if the man at Kennington Lane was Jeffrey Blackmore, then the man at New Inn was not.

But it was the latter who had signed the will.
Therefore the will was not signed by Jeffrey Blackmore; that is to say, it was a forgery.