Sir, said Arthur, and I will forgive you all the evil will that ever I ought you, an so be that you swear that upon a book before me.

With a good will, said King Mark; and so he there sware upon a book afore him and all his knights, and therewith King Mark and Sir Tristram took either other by the hands hard knit together.

But for all this King Mark thought falsely, as it proved after, for he put Sir Tristram in prison, and cowardly would have slain him.
Then soon after King Mark took his leave to ride into Cornwall, and Sir Tristram made him ready to ride with him, whereof the most part of the Round Table were wroth and heavy, and in especial Sir Launcelot, and Sir Lamorak, and Sir Dinadan, were wroth out of measure For well they wist King Mark would slay or destroy Sir Tristram.

Alas, said Dinadan, that my lord, Sir Tristram, shall depart.

And Sir Tristram took such sorrow that he was amazed like a fool.